Моя сила растёт каждый день.

Because сила is a feminine noun in Russian. The possessive adjective мой (my) has to agree with the noun it describes in gender, number, and case.

• masculine: мой
• feminine: моя
• neuter: моё
• plural: мои

So:

• мой брат = my brother
• моя сила = my strength

In Russian, nouns have grammatical gender. Сила ends in -а, which is a very common ending for feminine nouns, so it is feminine.

This is grammatical gender, not biological gender. A word like сила (strength) is feminine simply because that is how the noun behaves in the language.

In the present tense, Russian usually does not use a verb meaning is / am / are.

So English My strength is growing every day becomes simply:

• Моя сила растёт каждый день.

This is normal Russian grammar. The meaning of is is understood from the sentence structure.

Растёт is the 3rd person singular present tense of расти (to grow).

It is singular because the subject is сила (strength), which is one thing. So the verb must also be singular:

• сила растёт = strength grows / is growing

If the subject were plural, the verb would change:

• силы растут = strengths are growing

The dictionary form is расти.

Russian verbs are usually listed in the infinitive form, similar to English to grow.
Here is the pattern:

• infinitive: расти = to grow
• present: растёт = grows / is growing

This verb is imperfective, which fits an ongoing process like growing over time.

The letter ё is pronounced roughly like yo in yonder, though the exact sound depends on accent and surrounding sounds.

So растёт is pronounced approximately ras-TYOT.

A very important point: ё is always stressed in standard Russian spelling. That helps you know where the stress goes in растёт.

You may sometimes see растет written without the dots in informal texts, but it still means растёт and is pronounced the same way.

Каждый день means every day.

• каждый = every / each
• день = day

Together they form a common time expression meaning something happens daily.

So:

• растёт каждый день = grows every day / is growing every day

In this sentence, каждый день is being used as a time expression meaning every day. Russian commonly uses the accusative case for repeated time expressions like this.

Because день is an inanimate masculine noun, its accusative singular looks the same as the nominative singular:

• nominative: день
• accusative: день

And the adjective agrees with it:

• nominative masculine singular: каждый
• accusative masculine singular inanimate: каждый

So каждый день is the normal form here.

Yes. Russian present tense often covers both ideas.

• Моя сила растёт каждый день.

Depending on context, this can mean:

• My strength grows every day
• My strength is growing every day

English makes a stronger distinction between simple present and present continuous; Russian usually does not make that distinction in the same way.

Not necessarily. Сила can mean several kinds of strength, depending on context:

• physical strength
• inner strength
• power
• force

So Моя сила растёт каждый день could sound physical, emotional, motivational, or even poetic.

Yes, Russian word order is more flexible than English, though the neutral order here is:

• Моя сила растёт каждый день.

Other orders are possible, for example:

• Каждый день моя сила растёт.
• Растёт моя сила каждый день.

These may shift the emphasis slightly:

• Каждый день... puts focus on every day
• starting with Растёт... can sound more literary or emphatic

But for a learner, Моя сила растёт каждый день is the most straightforward and natural version.

The stress is:

• моя́
• си́ла
• растёт
• ка́ждый
• день

So the whole sentence is:

моя́ си́ла растёт ка́ждый день

Stress matters in Russian, because it affects pronunciation and sometimes even distinguishes different forms.

Yes. It is grammatically complete and natural.

It sounds like a normal sentence meaning that someone's strength is increasing over time. Depending on context, it can sound:

• neutral
• motivational
• dramatic
• poetic

So it works well both as a basic grammar example and as a real sentence someone might actually say.