Когда малышка засыпает, мама тихо выключает свет.

Because Когда малышка засыпает is a subordinate time clause introduced by когда (when). In Russian, clauses like this are normally separated by a comma:

• Когда малышка засыпает, мама тихо выключает свет.

This is true whether the когда-clause comes first or second:

• Когда малышка засыпает, мама тихо выключает свет.
• Мама тихо выключает свет, когда малышка засыпает.

Russian often uses the present tense for things that happen regularly or as a general pattern. Here the sentence means something like:

• Whenever the little girl is falling asleep, mom quietly turns off the light
• or When the little girl falls asleep, mom quietly turns off the light in a habitual sense.

So:

• засыпает = is falling asleep / falls asleep
• выключает = turns off

This is not necessarily about one specific moment happening right now. It sounds like a usual repeated situation.

Засыпает means is falling asleep or drifts off to sleep. It describes the process of going from awake to asleep.

Спит means is sleeping.

So the difference is:

• малышка засыпает = the child is in the process of falling asleep
• малышка спит = the child is already asleep

That is why засыпает is a very natural choice here: the mother turns off the light at the moment the child is drifting off.

Выключает is the imperfective verb, and it is used here because the sentence describes a habitual or repeated action.

• выключает = turns off, is turning off, does turn off
• выключит = will turn off

Russian perfective verbs do not have a true present tense. A form like выключит is future, not present.

So:

• мама тихо выключает свет = mom quietly turns off the light / usually turns off the light
• мама тихо выключит свет = mom will quietly turn off the light

Малышка is in the nominative case because it is the subject of засыпает.

• малышка засыпает = the little girl / little one falls asleep

Also, малышка is a feminine noun and often has an affectionate tone. It can mean little girl, baby girl, or simply little one, depending on context.

Свет is in the accusative case because it is the direct object of выключает:

• выключает что? → свет

For inanimate masculine nouns in Russian, the accusative singular is usually identical to the nominative singular. So:

• nominative: свет
• accusative: свет

That is why the form looks unchanged.

Тихо is an adverb meaning quietly, softly, or in a quiet way.

In this sentence it describes how the mother turns off the light:

• мама тихо выключает свет = mom quietly turns off the light

It does not mean that the light itself is quiet. It describes the mother’s manner or the quiet atmosphere.

That is a very natural position for an adverb in Russian. It directly modifies the verb:

• мама тихо выключает свет

Russian word order is fairly flexible, so other orders are possible, for example:

• Мама выключает свет тихо
• Тихо мама выключает свет

But these may sound less neutral or may shift emphasis. The original order is smooth and standard.

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

For example, these are all possible:

• Когда малышка засыпает, мама тихо выключает свет.
• Мама тихо выключает свет, когда малышка засыпает.
• Когда малышка засыпает, свет мама тихо выключает.
  This is possible, but marked and much less neutral.

The original version is the most natural neutral order. Putting the когда-clause first sets the time frame first, then gives the main action.

It can feel like either one, depending on context.

In a sentence like this, with both verbs in the present tense, когда often has a habitual sense close to whenever:

• Когда малышка засыпает, мама тихо выключает свет.
• Whenever the little one is falling asleep, mom quietly turns off the light.

But English often still translates it simply as when. The important point is that Russian present tense here can describe a repeated pattern.

The main stress is:

• Когда́ малы́шка засыпа́ет, ма́ма ти́хо выключа́ет свет.

A rough pronunciation guide:

• kag-DA ma-LYSH-ka za-sy-PA-yet, MA-ma TI-kha vy-klyu-CHA-yet svyet

A few useful notes:

• Unstressed о often sounds closer to a in real speech.
• засыпает has stress on -па-.
• выключает has stress on -ча-.
• свет is pronounced roughly like svyet.

Not exactly. Малышка is affectionate and specifically feminine in form. It often suggests:

• little girl
• baby girl
• little one

It comes from the idea of someone small or little. Compared with a more neutral word like ребёнок (child), малышка sounds warmer and more tender, which fits the sentence well.

Yes, if the subject is already clear from context, Russian can omit it more easily than English:

• Когда малышка засыпает, тихо выключает свет.

However, this would usually need context to sound natural, because the verb form выключает could mean he/she turns off. Including мама makes the sentence clear and complete on its own.