Learn Farsi: این سیب خیلی سفته.

The word سفته is a combination of the adjective سفت (firm) and the colloquial ending ـه (is). In formal written Farsi, this would be two separate words: سفت است. Because سفت ends in a consonant, colloquial Tehrani drops the beginning of است and attaches the rest as an "e" sound.

Why did we use سفت for a hard apple instead of سخت?

English uses "hard" for both concepts, but Farsi splits the meaning. Use سفت for physical firmness, stiffness, or tightness, like an unripe apple or a tight lid. Use سخت for things that are abstractly difficult (a hard exam) or materials that are rock-solid.

Why is the spoken "e" ending written with the letter "heh" (ه) in سفته?

In Farsi spelling, when a word naturally ends with an "e" or "a" sound, it is represented by a final silent "heh". When the spoken language shrinks است into a simple "e" sound at the end of a word, written colloquial Farsi adopts this same spelling rule instead of using a small vowel mark.

Does adding the ـه ending change how we pronounce the consonants before it?

Yes, it makes the word flow much easier. The word سفت ends in two consonants together. When you add the ـه vowel at the end, the final consonant connects to it, changing the rhythm from "seft" to "sef-te". This smooth flow is a big reason why Tehrani speakers shorten the word!