Learn Hardcore Russian: Не забывай поздравлять подругу. - Don’t forget to congratulate your friend female.

Because it’s the direct object of the verb. After поздравлять (кого? что?), you use the accusative case. Feminine nouns ending in -а/-я take -у/-ю in the accusative singular: подруга → подругу.

Why is it поздравлять and not поздравить?

Поздравлять is imperfective and fits habitual or repeated actions, which matches the reminder in Не забывай (“don’t forget (regularly)”). For a one-time event, use perfective: Не забудь поздравить подругу.

What’s the difference between Не забывай and Не забудь?

Не забывай (imperfective) = “Keep remembering; don’t neglect this as a habit.”
Не забудь (perfective) = “Don’t forget (this one time).”
Both are normal in Russian; choose based on whether it’s ongoing or a single occasion.

How do I say this formally or to more than one person?

Use the plural/formal imperative: Не забывайте поздравлять подругу. You can add politeness: Пожалуйста, не забывайте…

Do I need a possessive like “your” or “my”?

Not necessarily. Russian often omits possessives when context makes it obvious. You can add it for clarity: …поздравлять свою подругу (“your own female friend”), мою подругу, его/её подругу, etc.

How do I mention what I’m congratulating her on?

Use с + instrumental after the person: поздравлять подругу с чем?
Examples: с днём рождения, с победой, с окончанием университета, со свадьбой.

Can I use о (“about”) instead of с for “on/for”?

No. With congratulations, Russian uses с + instrumental, not о. Say поздравлять кого-то с чем-то, never “о чём-то.”

Can I replace подругу with a pronoun?

Yes: Не забывай поздравлять её. Here её is the accusative of “she/her” and will refer to the female friend from context.

Is the word order fixed?

It’s flexible for emphasis. Besides Не забывай поздравлять подругу, you might hear:

Не забывай подругу поздравлять.
Подругу не забывай поздравлять. All are grammatical; the default order is the most neutral.

How do I pronounce and stress it?

Stresses: Не забыва́й поздравля́ть подру́гу.
Notes: з in поздравлять stays voiced before д; ль is soft; дру́ in подру́гу carries the stress.

Does подруга mean “girlfriend” (romantic)?

Usually подруга means “female friend.” For a romantic girlfriend (in a typical hetero context), Russian uses девушка. Context can clarify, but подруга by itself is not automatically romantic.

What if the friend is male?

Use друг. As an animate masculine direct object, accusative = genitive: Не забывай поздравлять дру́га.

How do I make it plural (“friends”)?

Female friends: подруги (nom pl) → accusative plural (animate) = genitive plural: подруг.
Example: Не забывай поздравлять подру́г.
Mixed/male friends: друзья́ → acc pl (animate) = gen pl: друзе́й.
Example: Не забывайте поздравлять друзе́й.

Is “Не забудь поздравлять подругу” correct?

It’s grammatical but implies “don’t forget to congratulate her (as a habit/whenever appropriate).” More natural patterns are:

Habit: Не забывай поздравлять подругу.
One time: Не забудь поздравить подругу.

Could I simply say “Congratulate your friend!”?

Yes: Поздравь подругу! (informal singular), Поздравьте подругу! (formal/plural). That’s a direct command, stronger than the reminder “don’t forget to…”.

Why is it не and not ни?

Не negates verbs: не забывай. Ни can add emphasis in certain negative constructions but does not replace не before a verb. You might see both together for emphasis: ни в коем случае не забывай (“under no circumstances forget”).