I’m not sure that word is most commonly, or most accurately, translated as “zi”.
What about ci(yu) (词语)? When I’m looking up an English word in a “cidian” (dictionary), it will usually map to one “ci” in Chinese, which will be made up of any number of “zi” / characters (usually two or three).
I would normally translate word into zi. Google translate does too, but as chinese diaspora, maybe the mainlanders have more eloquent translations - Singapore did come from laborer stock after all.
词 (ci) I would normally translate as “phrase” or more commonly, (song) lyric. You wouldn’t ask someone, for example, what “ci” is this. You would however ask what “zi” is this. If you ask someone for “ci”, they would assume that you were asking where to find song lyrics.
I’m really struggling to think of a similar situation where I would use the english phrase “what word would I use here”. For example, if I were to translate the sentence “what word would I use to describe being happy” into chinese, it would be “kai xing de gan jue yao je mo biao da”, or literally, “happiness the feeling how do (I) express”. Saying “kai xing de gan jue yong she mo zi (or ci) lai biao da” (literally, happiness the feeling use which word (or phrase) to express) sounds very awkward to me. If I did ask that, I would expect the answer to be a single zi (maybe le), or if ci, it would be a poetic phrase of some sort.
EDIT: I’m also more familiar with calling it a zi dian, rather than a ci dian, but both are used.
EDIT2: I checked google translate again, and ci is the second translation of “word”. It also translates ci to “term, speech, statement”, so a bit longer than just word. I’m still struggling a bit with it. 
As does baidu translate, but interestingly when it gives example sentences using the word “word” it then proceeds to use ci for the majority.
OTOH a list of new vocabulary would be “shengci”, verbs are “dongci”, nouns are “mingci” etc.
I immediately thought of that after I posted. Particularly xing rong ci (adjective). Still, I hardly ever hear people use “ci” by itself, and I briefly asked by colleagues whether they would consider the words “tai wan ren” to be a “ci”, and got looked at like I grew a third head.
I’ve never used “ci” in speech alone either; always ciyu.
And it’s always passed the basic “be understood” test…which a lot of rules of thumb (including some taught to me by Mandarin teachers) do not.
But I don’t claim to be an expert on this…I’m just trying to get it as clear as possible.
I was just reminded by my wife of ciyu. So I guess you’re right! I would still prefer translating word as zi and phrase as ci though, since each zi has individual meaning and a ci is more akin to a collection of words than a single idea. More like a German style compound word.
On a related note, I’ve had lengthy discussions with Chinese friends about accents in written Chinese. It stemmed from a translation of Huckleberry Finn, and I wanted to know how the debased English was represented (e.g. “sho’ nuff” for “sure enough” - that kind of thing). Turns out, it was just omitted - there was no way of rendering such things in Chinese.
What Chinese can do, however, that English cannot, is layer words with a sort of pictorial quality. Given, for example, a choice between two adjectives, one based on the ‘metal’ radical and one based on the ‘heart’ radical, the choice made is significant on an interesting level. The former might conjure additional images of steeliness and strength, the other warmth and sensuality. Hard to get the same nuance with an alphabet.
Now this makes sense. My limited understanding of this is that all the Chinese dialects use the same written form for words, and if that is correct obviously makes it impossible to use Chinese to write in dialect.
It has advantages though.
For example, chinese has no verb conjugation, very few plurals, simple number system (they have no “and”, “teens” or suffixes; 483 would be “Four hundred eight ten three”)
This all makes sense given a writing system that cannot easily describe contextual differences in pronunciation (though admittedly this is a WAG).
Relevant:
http://www.pinyin.info/readings/texts/chinese_writing_reform.html
An article (complete)
*Sound and Meaning in the History of Characters:
Views of China’s Earliest Script Reformers
*
Victor H. Mair
University of Pennsylvania
http://www.pinyin.info/readings/texts/chinese_writing_reform.html
Taken from
Difficult Characters: Interdisciplinary Studies of Chinese and Japanese Writing
edited by
Mary S. Erbaugh
Chapter titles, authors here: Difficult Characters: Interdisciplinary Studies of Chinese and Japanese Writing
This is actually not completely true. Singaporean Hokkien, for example, uses certain old Chinese characters to represent certain words, and these old Chinese characters are no longer in use in common mandarin these days. If shown to a modern day speaker of Chinese, they would appear to be nonsense.
More info here Singaporean Hokkien - Wikipedia