In addition to that, phrase and expression have additional strictly grammatical meanings. So that a phrase consists of typical two or more words (what Kate Gregory mentions). A phrase can be a sentence but usually is not. An expression is the more general case and can be a word, phrase or sentence

So at the end, actually "idiom" has the clearest definition (established meaning not directly linked to the individual words).

First, I want to thank you @Bogdan for emphasizing this question. I tried to do what others did, and classify the three terms using a transitive relationship. Not quite that simple. The more I thought about this, the closer I got to erasing my entire answer and giving up! In response to your fine comments: I did not say that phrases (such as "needless to say") were random combinations of words, not semantically linked. But I remember reading that on ESL yesterday, yet can't find it now! Kate Gregory conveyed better what I meant re categorizing phrase vs expression as sentence or fragment.

@Bogdan con't I will clarify that part of my answer accordingly. Also the grammatical definition via your citation is sensible, I will incorporate that too.

Please don't erase it-note that this question had a bounty from me and you got it. I didn't say your phrase was random, on the contrary, I wanted to emphasize that it is not. So from your comment I see that you wanted to say the same thing about phrase as Kate Gregory(I misunderstood before that you diverged on that point). So now I see what you meant by semantical (which is the same as what I meant by grammatical). But note phrase could in addition mean idiomatic phrase. So there are two meanings of "phrase" and "expression".

@Bogdan Thanks again for clarifying. I was wondering if I should alter an answer which was bequeathed a bounty (sorry, but I'm a relative novice here, so am very happy and excited). My knowledge of grammar is not as good as it could be. Thus some terms like phrasal idioms are unfamiliar to me. Studying Latin (or recalling French grammar better than I do) is almost de rigeur <grin> for being able to articulate grammatical constructs. This last comment is off topic, I will delete it after a brief while, after I think you have seen it. <Idle thought: I wonder if there is IM or IRC here?>

This is my first time here. StackExchange has the most wonderful user interface! This is amazing!

hi, yes, SE has a great user interface

I really like it! So elegant.

Better than IRC, which is why I was surprised by the notes, people requesting IRC or XMPP.

I like this better!

there is also a chat for everybody at ELU

Really??? Not just separate topics?

Ooooh! Cool. Thank you. ;#)

there are rooms for one to one like this

it's like IRC, yes

I just added a star to that! The mass room. But this is so smooth and pleasant compared to IRC.

Maybe that's because I'm using Chrome and a better computer!

Than in the past, though.

sure, it is much better than IRC

I see you use Mathematics SE. I have a Math undergrad degree, yet

most of the questions are beyond my ability!

or Yahoo Answers or any other Q&A sites I saw

Oh yes, definitely. Do you use Quora? Another Q&A site.

no

I think stack exchange is superior to Quora

I am a Math graduate too

Have you heard of it? I used to enjoy Yahoo Answers, even if it was silly sometimes. What degree in Math do you have? Grad?

Master degree

I got my Master's degree in Operations Research. I didn't like real analysis, set theory urg. I like DiffEQ's, PDiffEQ's, complex analysis, Fourier transforms, LaPlace, LaGrange, Stokes, that sort of thing. And probability, queueing theory, random numbers prob distrib's. What kind of math do you like?

I used to do abstract algebra, but now more interested in probability and stats

you can see I am on Stats SE too

Abstract algebra! Linear algebra, yes those are difficult for me. Probability and statistics are what I like best, and have done. Are you still in school?

no, I worked as a tutor last year

I didn't notice Stats SE, I just saw an abbreviated version of your profile which highlighted cooking SE actually. Maybe that only pertained to your chat activity, and not overall SE.

I need to find work again. It is difficult in the U.S. now.

hehe that's right

yeah, I understand

I think I'll have a look at the mass chat area. And make sure I didn't mess up my answer when I ported it here to chat.

and me I need to find work or study again

I haven't seen you on English SE before. Mostly same people here all the time. I really need to find work, I'm running out of money.

This is my fun place, forget about my troubles here!

hmm

what do you mean before?

btw I am the same as the one that bugged you at that bounty question

i don't know if you realize that

What in particular do you refer to? Ohhh, okay. You are Bogdan?

yes

Ohhhh! Okay! I always have trouble with names and alt's!

lol

You speak other languages besides English, I think, but your knowledge of English subtleties is very impressive.

thank you,

And of grammatical constructs in general. That is what I meant when I said what I did about learning Latin. English has no cases, is in many ways an easy language.

You also perceived all those little nuanced meanings I gave in my example of expressions (or was it phrases!)

i don't know what happens with the bounty if you edit it

but the way it is now is ok

besides one can read my comments

I was afraid to edit it, did not want to do so and thus lose the bounty!

But I didn't know what the proper protocol was.

at least I myself I came at some understanding

And I also did not want to seem too effusive in thanking you in the comments. Did you really, come to a greater understanding?

Your understanding was quite good, but maybe the process of

certailnly

articulating it with us is what consolidated and strengthened it. I liked

your comment about the existing answer not being the Platonic ideal of an answer

to Simchona, I think that is the name. I laughed a bit at that. It was a nice way of putting it.

I think it was a complex question

It is actually one of the better questions on English stack exchange, in my opinion.

It is appealing logically, because of the partially transitive relationships between the terms

yes, but common people do not clearly see those boundaries

Yet it also has some of the je ne sais quoi pas of human language, that is not so readily quantified. I liked it a lot.

True. I know what you mean.

Most of the time life is like that for me.

there were some math questions whose answers could be interpretted formally (as in mathematics) or informally, (as in common language)

I find all sorts of things interesting or charming but no one else appreciates the symmetry, or allusion, or humor or irony of it.

Really? That sounds VERY fun! The math questions to which you refer.

yes

Are they still there, or did they get removed as not acceptable?

they are

Tell me please? Where? URLs

If you would be so kind, or a way to search for them?

sure, wait

I don't want to impose on your goodwill.

Okay!

I'll be here, take your time.

english.stackexchange.com/questions/tagged/mathematics

Ohh, that is interesting. There were moved over from Math to English?

Yes! That is a good one. Infimum etc. I actually saw the annulus question a few days ago!

no, some ask Math question to ELU

Annulus is a very challenging word to use without silliness ensuing....

I used to tell them to move but gave up

To make an analogy, I was surprised at the number of Finance questions asked in StackOverflow and SuperUser.

Questions about finding real-time stock quotes etc.

well I suppose that is of general interest

I just thought of another Math-English question: What is a saddlepoint? Or point of inflection? I always liked those terms from a purely math point of view.

But that isn't really the right sort of thing for English SE.

My idiomatic understanding tells me that! Right?

you can ask what is the etymology of saddlepoint in math

Ahhh, okay! That would do it. A good way of approaching things.

though it can be something about the history of math

Will you tell me what country you are in now? I am always curious about things.

if you really want to, you can ask in math SE

Serbia, Romania?

Yes, I think it would make more sense in Math SE to ask as a math history question rather than etymology.

Romania

you guessed

Makes sense. All the umm diacritical marks in your name. Also, Romanian is the closest language to Latin. Well maybe the Romanch spoken in eastern Switzerland, you think?

Is Romania a lot different from Serbia?

I don't think Romanian is the closest though I would want to

Romanian has many Slavic influence

I suppose some features of Latin are preserved in Romanian, which may be surprising

why Serbia in special?

What do you think is closest? Italian? Regarding Serbia. Well,

there is someone mysterious that I know there. Or have deduced is there. And I know nothing of the country other than what is available online, which is not representative.

I don't think. I'm not sure. Serbia is far far away from where I am. I'm in Arizona.

But I travelled with my family to Switzerland, to Lugano and Interlaken and Flims and Zurich years ago.

And they speak Romanch there. Which my father said was

I think depends on what you mean by closest. Some features of Latin such as grammar, or vocabulary or syntax are preserved in some Romance languages but not in others

similar to Latin. He spoke English and French and German, but was able to communicate best with the local people in Latin!

But only in that one part of Switzerland. It is a regional dialect Romansch , I am probably mispelling it!

The German spoken in Zurich is a different, um "low German" than in Munich of Berlin. Nothing wrong with it, and I don't even speak it. Just heresay.

well Serbia shares some common things with Romania, they are neighbours, Balkanic culture,

Spanish is one of the easier Romance languages. French is not so easy. 14 verb tenses. All sorts of little rules. Italian is supposedly not so difficult.

the language is very different though

Tell me more please. How are the languages different?

both countries were communist in the same sphere of influence

Romanian is more Latinate, but Serbian has more Russian, Slavic or Turkic influence?

in fact it is said Romania and Serbia were always friend countries

Yugoslavia, Tito. Yes, Balkans

unlike other neighbours of Romania\

Serbian is a Slavic language, I suppose Turkish influences are the same

Bulgaria (umm Zagreb?) was always a challenge. Now there are so many new Balkan countries. Bosnia Herz etc

What kind of infrastructure is there in Serbia? Decent internet?

Not like Georgia, for example?

it is not in European Union

Russia Georgia.

Is Romania in the EU?

yes

Serbia was attractive to Romanians before the fall of communism but the war in the 90s was very damaging

the war left it in shatters

Serbia has still not recovered from the ravages of war in the 90's?

another thing is that both Romania and Serbia are Orthodox countries

that is they have the same majoritary religion

Greek Orthodox. Eastern Holy Roman Empire. Not Muslim.

yes, I think Serbia is not fully recovered

there is also the international trust which was missed

It takes years for any country, particularly one that is not wealthy due to exogenous factors, to recover form civil war or other war disruption. Libya is an exception, sitting on all that sweet light crude oil. Serbia is not blessed with anything similar.

And int'l community will help Libya more, because they want Libya's oil.

hehe

Trust will not even be necessary. But Serbia, Chechnya, maybe Lebanon one day, it will take a long time, I think. The Colonel (Gahddaffi) is actually quite amazing. He held out for over six months.

He is quite a acharacter

The leaders in those other countries in North Africa, well Tunisia and Egypt, fled within weeks. I am amazed Ghaddafi lasted so long. Unfortunately, as a result, there was probably much greater loss of life. Sigh.

He IS a character, isn't he?

He is like a clown sometimes but still manages to hold strength

I used to loathe him. But then I heard that he did do things that benefited the Libyan people quite a bit initially, when they gained complete independence from Italy (and others) decades ago.

not clown

like one who does buffoneries

I really don't know how he stays so strong. He is not young.

He just seems like a clown, a bit. I think he is probably very savvy, much more so than someone like Sadaam Hussein.

oh yeah

he is more savvy

Ghaddafi is not a clown at all. I don't think he is irrational particularly. As in religious fervor distorting his decisions (I refer to Ghaddafi).

like one day he says "rebels are rats"

next day tries to negociate with them

i think he appeals to the short memory of the masses

Six months is a VERY long time to hold out against NATO bombing and a civil war, yet he did it.

we can see that is contradictory but the masses forget easily

That must be it , because he could not rule based on fear alone, like a typical autocratic, fascist or totalitarian dictator, you know?

though some of his oratory is quite bizzare

Yes! It is! His retinue of women is actually rather logical. Not as strange as it would seem. But yes, bizarre oratory, that is quite fitting.

It is strange that he does that, yet behaves so strategically and is sometimes so clever.

yes

I need to depart now. Is Mielu your chat room name only?

yes

I am Ellie. But Feral Oink everywhere else on SE.

bye bye then

ok Ellie

It has been a pleasure to meet you, and talk with you today. Truly. Very formal of me.

Bye for now!

nice to meet you too