Learn Hardcore Russian: Мне холодно, поэтому я надену свитер.

Мне холодно literally means To me (it is) cold, and it’s the most natural way to express a temporary physical sensation (feeling cold right now). Russian often uses this pattern: dative pronoun + word of state.

Мне холодно / жарко / страшно / скучно / больно = I’m cold / hot / scared / bored / in pain. Я холодный usually describes a quality of a person/thing (e.g., I am a cold person emotionally, or I am cold to the touch). For weather you’d say На улице холодно.

What case is мне, and why is it used?

Мне is the dative case of я. In constructions like Мне холодно, the dative marks the “experiencer” (the person who experiences the state). Compare:

Мне холодно = I feel cold.
Ему грустно = He feels sad.
Нам интересно = We find it interesting.

What part of speech is холодно here?

Холодно is a word of state (often taught as a predicative adverb / category of state). It functions like a predicate without a normal verb to be:

Мне холодно = (I am) cold / I feel cold.
Здесь холодно = It’s cold here.

Why is there no verb meaning to be in the sentence?

In the present tense, Russian usually omits быть (to be). The meaning is understood:

Мне холодно = (I am) cold. If you need past/future, быть can appear:
Мне было холодно = I was cold.
Мне будет холодно = I will be cold.

Why is there a comma before поэтому?

Because поэтому (therefore/so) connects two independent clauses:

Мне холодно, поэтому я надену свитер. This is the standard punctuation: comma before поэтому when it introduces the result clause.

Can I replace поэтому with так что or потому что?

Yes, but the meaning/structure changes:

..., поэтому ... = ..., therefore ... (result)
..., так что ... = ..., so ... (result, often more conversational)
... потому что ... = ... because ... (gives the reason clause) Examples:
Мне холодно, поэтому я надену свитер. = I’m cold, so I’ll put on a sweater.
Я надену свитер, потому что мне холодно. = I’ll put on a sweater because I’m cold.

Why is надену used (not надеваю or буду надевать)?

Надену is perfective, so it expresses a single completed action in the future: I’ll put it on (once).

Я надену свитер = I’ll put on a sweater (one action, decision/result). If you want an ongoing/repeated idea, you’d use imperfective:
Я надеваю свитер (когда холодно). = I put on a sweater (habitually) / I’m putting on a sweater (right now, depending on context).
Я буду надевать свитер. = I will be putting on / I will wear (as a process/habit in the future context).

How does Russian form the future in я надену?

Perfective verbs form the future with present-tense endings that have future meaning. So надеть (pf.) → я надену = I will put on. With imperfective verbs, the future is usually буду + infinitive:

надевать (impf.) → я буду надевать.

What’s the difference between надеть and одеть?

A common rule:

надеть = put on (something on yourself): надеть свитер/шапку/пальто
одеть = dress (someone): одеть ребёнка = dress the child
So я надену свитер is correct: you’re putting a sweater on yourself.

Why is свитер in that form—what case is it?

It’s accusative (direct object of надеть).
Свитер is masculine inanimate, so accusative = nominative:

свитер (Nom.) → свитер (Acc.) Compare with an animate masculine noun where accusative changes:
Я вижу брата. (Acc. = Gen. for animate)

Can Russian drop я here?

Yes. Russian often omits subject pronouns when the verb ending already shows the person:

Мне холодно, поэтому надену свитер. Including я adds a bit more emphasis/clarity, but both are natural.

How should this sentence be pronounced (stress)?

Common stress:

Мне хо́лодно, поэ́тому я наде́ну сви́тер. Approximate pronunciation cues:
мне ≈ mnye
хо́лодно ≈ KHOL-ad-na
поэ́тому ≈ pa-eh-TA-mu
наде́ну ≈ na-DYE-nu
сви́тер ≈ SVEE-ter