The difference between "пойди", "иди" and "начни идти"?

Question

What's the difference between "пойди", "иди" and "начни идти"?

"Иди" is imperfective, while "пойди" and "начни идти" are perfective. However, as far as I know, both "иди" and "начни идти" are used in the sense of "Start going!" or "Start walking!".

It's interesting that if we turn "пойди" and "начни идти" into infinitives, then they will both mean the same thing: "пойти" = "начать идти". However, the imperative forms seem to show some difference in their usage.

For one, is that "пойди" is, according to my observation, never used in the sense of "Start walking!" - the form "пошёл" is used in such case instead ("Пошёл!").

Another difference that I can sense here is that "пойди" always requires some additional modifier. Usually it's a modifier that adds some info about the purpose for the action of going/walking: "Пойди к Сергею.", "Пойди за молоком.", "Пойди на концерт."

"Начни идти", however, doesn't need any such modifier and sounds complete as it is.

Are there any other nuances that I don't see?

EDIT: Please, note that I am not asking about "сходи" or any other words! I am only asking about the words that I mentioned in my question.

Answer 1

While "начни идти" is grammatically correct, it sounds artificial. I rather can imagine more usable phrase "начинай идти", but I think no one talks like that in usual situations.

Answer 2

Начинай or начни идти is not common, but can be used in certain situations. For example, when you are trying to time (e.g. shooting a video) or closely watch (e.g. counting steps, evaluating gait) someone's walking, then you can say начинай идти to alert the person to start moving.

By the way, "Пошёл!" could be used in such situations too (sporting events, competitions), but it won't necessarily apply to walking actions only, but also to running, swimming, horse-riding, etc. "Пошёл!" is less formal, more imperative than иди, and sometimes rude (when used in Go away! meaning).

Answer 3

"Пойди" and "Иди" would be incomplete without the mention of "Сходи" (meaning "Go somewhere and get back"). If the teller's intention is not to essentially get rid of someone, "сходи" is the most common form (unless the destination is teller's own location - in that case "подойди" or "зайди" is common).

• "Пойди за молоком" - almost never used;
• "Иди за молоком" - "Go get milk already!" (stress on "Go!");
• "Сходи за молоком" - "Go get milk" (neutral)

The other construct is "Пойди/Иди/Сходи to do something (verb)". With the verb, all three forms can be used quite widely.

• "Пойди пообедай" - "Go to lunch";
• "Иди пообедай" - Also "Go to lunch", but little less polite and more imperative;
• "Сходи пообедай" - most polite of these forms.

There is also a short form of "пойди" - "поди". "Поди" is used broadly in a number of phrases (ex. "Поди прочь!"), and also often as an adverb.

"Начинай идти" is not a commonly used phrase. I can think only of some specific situations where it can be encountered, like a stage director is addressing the actor.