Learn Hardcore Ukrainian: Моє серце спокійне.

It translates literally to My heart is calm. The sentence expresses that the speaker’s heart (or inner self) is in a state of calmness or tranquility.

Why is there no verb equivalent to "is" in the sentence?

In Ukrainian, the present tense of the verb to be (бути) is typically omitted. The sentence Моє серце спокійне implies "My heart is calm" without explicitly stating the copula is.

Why does the adjective appear as спокійне instead of спокійний or спокійна?

Adjectives in Ukrainian must agree with the noun they modify in gender, number, and case. Since серце (heart) is a neuter noun, the adjective takes the neuter ending -не, resulting in спокійне. Using спокійний (masculine) or спокійна (feminine) would be incorrect.

Why is the possessive pronoun моє used instead of мій?

Possessive pronouns, like adjectives, must agree with the noun in gender and number. Серце is neuter, so the neuter form моє is used. In contrast, мій is the masculine form and would be used with masculine nouns.