Он подошёл сзади.

Подошёл is the masculine singular past-tense form of подойти.

Подойти means to come up to, to approach, or to walk up to someone or something. So он подошёл means he came up / he approached.

This verb has an irregular past form.

The infinitive is подойти, but in the past tense the stem changes:

• подойти → подошёл (masculine)
• подошла (feminine)
• подошло (neuter)
• подошли (plural)

This is something you mostly just have to learn as a verb pattern.

Also, the ё is important here: подошёл.

In Russian, past tense is usually formed with -л plus gender/number endings.

For this verb:

• masculine: подошёл
• feminine: подошла
• neuter: подошло
• plural: подошли

Since он means he, the masculine form подошёл is used.

Подойти is perfective.

That means it presents the action as a single completed event: he came up, and the approach was completed.

The imperfective partner is подходить:

• Он подходил сзади = he was coming up from behind / he used to come up from behind / he approached from behind in a non-completed or repeated sense
• Он подошёл сзади = he came up from behind, completed

So this sentence describes one completed action.

Because подойти is more specific.

• идти = to go / to be walking
• прийти = to come / arrive
• подойти = to come up to someone/something, to approach

So подойти focuses on moving up to a person or place, not just moving in general.

In this sentence, the idea is not just that he was walking, but that he came up from behind.

Сзади means behind, at the back, or from behind, depending on context.

With a motion verb like подошёл, the most natural meaning is from behind:

• Он подошёл сзади = he came up from behind

So сзади tells you the direction or position of the approach.

In this sentence, сзади is an adverb, so it does not have a case ending.

That is why it stays the same.

You can also see сзади used with a noun in expressions like сзади дома (behind the house), but here by itself it is simply an adverb meaning behind/from behind.

Russian often leaves that unstated if the context already makes it clear.

So Он подошёл сзади can naturally mean:

• he came up from behind
• he approached from behind

If you want to say exactly behind whom, you can add it:

• Он подошёл к нему сзади = he came up to him from behind
• Он подошёл к ней сзади = he came up to her from behind

The original sentence is normal if the listener already knows who or what is involved.

Yes. Russian word order is flexible.

The neutral order here is:

• Он подошёл сзади.

You could also move things around for emphasis:

• Сзади он подошёл.
• Подошёл он сзади.

But these sound less neutral and would usually depend on context. For a simple basic statement, Он подошёл сзади is the most straightforward word order.

Yes, Russian can sometimes omit subject pronouns when the subject is already obvious from context.

So in a story, you might see:

• Подошёл сзади.

But as a standalone sentence, он helps make the subject clear:

• Он подошёл сзади.

So the pronoun is not unusual here at all.

It is pronounced approximately pada-SHYOL.

A few useful points:

• the stress is on ёл
• ё is always stressed
• many printed texts write е instead of ё, so you may sometimes see подошел, but it is still pronounced подошёл

For learners, remembering the stressed ё here is very helpful.

They are similar, and both can mean behind.

But сзади is very common in everyday speech, and in this sentence it sounds especially natural:

• Он подошёл сзади.

Позади is also possible in some contexts, but it can sound a bit more formal or simply different in nuance.

For this exact sentence, сзади is the most natural everyday choice.

Yes, there can be a little overlap in interpretation.

With сзади, the sentence most naturally suggests from behind. But depending on context, it can also imply that he approached so that he ended up behind someone.

In normal use, though, most learners should understand Он подошёл сзади as:

• He came up from behind.