See also:ۃ [U+06C3 ARABIC LETTER TEH MARBUTA GOAL], ۀ [U+06C0 ARABIC LETTER HEH WITH YEH ABOVE], ۂ [U+06C2 ARABIC LETTER HEH GOAL WITH HAMZA ABOVE], ہ [U+06C1 ARABIC LETTER HEH GOAL], ه [U+0647 ARABIC LETTER HEH], andھ [U+06BE ARABIC LETTER HEH DOACHASHMEE]
It mostly exists in grammatically feminine words. It always follows a fatḥaـَ ("a"), and it is replaced with a normal ت (tāʾ) when a suffix is added, e.g. غُرْفَة (ḡurfa, “a room”) -> غُرْفَتِي(ḡurfatī, “my room”) (غُرْفَة (ḡurfa) (ة -> ت) + ـِي (-ī)).
When desinential inflection is used in Classical Arabic or in formal Modern Standard Arabic, non-pausal ة is pronounced as /t/ (preceded by usually unwritten fatḥa "a") and has -u/un, -i/-in, -a/an case endings, e.g. لُغَةٌ - "luḡah" (pausal), "luḡatun" formal, non-pausal pronunciation (nominative case, indefinite).
Adverbials from tāʾ marbūṭa do not add alif (ا) with fatḥatān. Instead, fatḥatān is attached directly to tāʾ marbūṭa and the "hidden t" is pronounced with the ending "-an" e .g. عَادَةً (ʿādatan, “usually”).
In a more relaxed orthography ة is replaced with ه (hāʾ) with the same pronunciation, especially in Egypt and Sudan.
Loanwords in other languages (e.g. Persian or Turkish) from words with tāʾ marbūṭa use the endings at, et, ah, a or e.