Learn Turkish: Yardımın yeterli, teşekkürler. - Your help is enough, thank you.

The base word is yardım (help). The -ın at the end is the possessive suffix for "your" (informal, singular). So, yardımın literally means "your help".

Where is the word for "is" in this sentence?

In Turkish, the "to be" verb (am/is/are) is often completely invisible in the third person. The adjective yeterli (sufficient) stands alone here, but the sentence is naturally understood as "is sufficient" or "is enough".

What is the difference between yeter and yeterli?

Yeter usually acts as a verb ("it suffices") or a standalone exclamation ("Enough!"). By adding the suffix -li (which turns nouns into adjectives meaning "with" or "having"), it becomes the adjective yeterli, which means "sufficient" or "adequate".

Why does teşekkürler have the plural suffix -ler?

Teşekkür is a noun meaning "gratitude" or "a thank you". Just like in English where we say "thanks" in the plural, Turkish adds the plural suffix -ler to make teşekkürler. (You will also often hear teşekkür ederim, which means "I give thanks").