Привяжи собаку к дереву.

The dictionary form is привязать.

• привяжи = singular informal imperative: tie! / fasten!
• It is the command form used when speaking to one person you address informally.

So:

• привязать = to tie, to fasten, to attach
• привяжи = tie! / tie it!

This is a normal stem change in Russian verb formation.

With привязать, the imperative is formed from the stem in a way that gives:

• привязать
• привяжу = I will tie
• привяжи = tie!

The з changes to ж in some forms. This kind of consonant alternation is common in Russian.

So although привяжи may look quite different at first, it still belongs to привязать.

Because собаку is the accusative case, and it is the direct object of the verb.

The sentence answers the question Tie whom? → the dog

For a feminine noun ending in -а, the accusative singular usually changes:

• собака = dog
• собаку = dog (as the direct object)

So:

• собака is nominative
• собаку is accusative

Because the preposition к requires the dative case.

• дерево = tree (nominative)
• к дереву = to the tree / onto the tree / up to the tree in the sense of attachment

In this sentence, к дереву expresses what the dog is being tied to.

So the pattern is:

• к + dative
• к дереву

In this sentence, к means something like to in tie the dog to the tree.

More literally, it marks direction or attachment toward something.

Examples:

• идти к дому = go toward the house
• подойти к окну = come up to the window
• привязать к дереву = tie to a tree

So here к does not just mean physical movement; it can also show that one thing is being attached to another.

Because those would mean different things.

• к дереву = to the tree, attached to the tree
• на дерево = onto the tree
• у дерева = by the tree / near the tree

If you say Привяжи собаку к дереву, the dog is tied to the tree.

If you said у дерева, that would suggest location near the tree, not attachment. If you said на дерево, that would sound like tying something onto the tree in a different spatial sense.

So к дереву is the natural choice with привязать.

Yes, it matters. привяжи comes from the perfective verb привязать.

Perfective verbs usually focus on the action as a completed result:

• привяжи собаку к дереву = tie the dog to the tree, so that it ends up tied

The imperfective partner is usually привязывать or, in imperative use, often привязывай:

• привязывай собаку к дереву can sound more like:
  • do the tying
  • tie the dog (process / repeated instruction / general instruction)

In many commands, the perfective imperative sounds natural when you want a single completed action.

Use привяжите.

• привяжи = singular informal
• привяжите = plural or polite singular

So:

• Привяжи собаку к дереву. = Tie the dog to the tree. (to one friend, child, etc.)
• Привяжите собаку к дереву. = Tie the dog to the tree. (to several people, or politely to one person)

The stress is:

• привяжи́
• соба́ку
• к де́реву

A rough pronunciation guide:

• привяжи́ ≈ pri-vya-ZHEE
• соба́ку ≈ sa-BA-koo
• к де́реву ≈ k DYE-ri-vu

A few notes:

• я after a consonant often softens it
• ж is like the s in measure
• unstressed vowels are often reduced in pronunciation

Yes. Russian word order is more flexible than English word order because case endings show grammatical roles.

The neutral order here is:

• Привяжи собаку к дереву.

But you may also hear:

• Собаку привяжи к дереву.
• К дереву привяжи собаку.

These versions can change the emphasis:

• Собаку first may emphasize the dog
• К дереву first may emphasize to the tree

Still, the most straightforward version for a learner is:

• Привяжи собаку к дереву.

Russian has no articles like a or the.

So собаку can mean:

• a dog
• the dog

And к дереву can mean:

• to a tree
• to the tree

The exact meaning depends on context.

In this sentence, English usually uses the dog and the tree if both are already known in the situation, but Russian does not need separate words for that.

Not as a normal direct command by itself.

• привяжи собаку к дереву = direct command: Tie the dog to the tree
• привязать собаку к дереву = infinitive: to tie the dog to the tree

The infinitive can appear in certain contexts, for example:

• on a sign
• in instructions
• as a harsher, more official-sounding command in some situations

But if you are directly telling one person to do it, привяжи is the normal form.

Usually the thing used as the means or instrument goes in the instrumental case.

For example:

• Привяжи собаку верёвкой к дереву. = Tie the dog to the tree with a rope.

Here:

• верёвка = rope
• верёвкой = with a rope (instrumental)

So in a fuller sentence you can see three important patterns:

• собаку = accusative, direct object
• к дереву = dative after к
• верёвкой = instrumental, means/tool

This makes the sentence a very useful example of how Russian cases work together.