Заходи как-нибудь.

Заходи is the informal singular imperative of заходить.

• заходить = an imperfective verb
• заходи = come in / drop by when speaking to one person you address as ты

So the sentence is addressed casually to one person, such as a friend, relative, or someone you know well.

Russian has different imperative forms depending on who you are talking to.

• заходи = to one person, informal
• заходите = to more than one person, or to one person politely

So:

• Заходи как-нибудь. = casual, to one friend
• Заходите как-нибудь. = polite or plural

This is similar to the ты / вы distinction in Russian.

Here как-нибудь means sometime, one of these days, or when you get a chance.

That is different from another common meaning of как-нибудь, which can also mean somehow in other contexts.

In this sentence, it does not mean come in somehow. It means something like:

• Drop by sometime.
• Come over one of these days.

So the time is intentionally vague and non-specific.

In Russian, the subject is often omitted when it is obvious from the verb form.

Because заходи is an imperative, it already tells you:

• the sentence is a command/invitation
• it is directed at you
• it is directed at one person informally

So Russian does not need to say ты here.

A version with ты would usually sound unnecessary unless you wanted special emphasis.

In this context, заходить means to come by, to stop in, or to drop by.

The verb comes from ходить (to go, to walk) with the prefix за-, but in modern everyday usage заходить often functions as a set expression for visiting briefly.

So Заходи как-нибудь is a very natural way to invite someone to visit.

Depending on context, заходить can also mean:

• to go in / enter
• to stop by
• to drop into a place

Here the visiting sense is the important one.

This is a very common learner question, because both forms may seem possible.

• заходи = imperfective imperative
• зайди = perfective imperative

In invitations like this, заходи often sounds more natural because it has a friendly, open-ended feeling:

• Feel free to drop by sometime
• Come by whenever

It can suggest that the action is not tied to one sharply defined occasion.

Зайди как-нибудь is also possible, but it can sound a bit more like make sure you come by at some point or drop by sometime on one occasion.

In many everyday situations, the difference is subtle, but:

• заходи как-нибудь = warmer, looser, more habitual/open invitation
• зайди как-нибудь = more focused on one completed visit

It can be either, depending on tone, relationship, and situation.

Often it works like English:

• Drop by sometime.
• Come over sometime.

Sometimes that is a genuine invitation. Sometimes it is just a friendly social formula and not a concrete plan.

So learners should not automatically assume it means:

• I definitely expect you soon
• Let’s schedule something now

If a Russian speaker wants to make it more concrete, they might add a time or suggestion, for example:

• Заходи как-нибудь на выходных.
• Заходи в гости в субботу.

Without that, the sentence often stays pleasantly vague.

No. Как-нибудь has more than one common meaning.

1. sometime / one of these days

   • Заходи как-нибудь.

2. somehow / in some way

   • Мы как-нибудь решим эту проблему.
     = We’ll solve this problem somehow.

So you have to read it from context.
With an invitation like Заходи как-нибудь, the time-related meaning is the natural one.

Normally, no comma is needed.

Как-нибудь is just an adverb modifying the verb заходи, so the sentence is written as:

• Заходи как-нибудь.

You might see punctuation changed only for special expressive reasons in informal writing, but the standard version has no comma.

It is very natural and common.

A native speaker could say this to a friend after meeting them, talking at the door, or ending a conversation. It sounds friendly, casual, and idiomatic.

Very close English equivalents are:

• Drop by sometime.
• Come over sometime.
• Stop by one of these days.

So this is a useful phrase to remember as a whole expression, not just as separate words.