What is the difference between "رحمت" and "رحمة" in the Noble Qur'an?

The word (رحمة - rahmah) appears in the Holy Quran seventy-nine times. It is written with an open ta (ت) in seven instances, and with a rounded ha (ـه) in all other instances. Scholars have differed in explaining this variation in spelling, offering several opinions: that it was written according to its original form, which is the ta; or with the intention of joining; or that stopping with the ta is consistent with the dialect of a group of Arabs, such as Tayy; or to preserve its form in ancient orthography. There is no semantic difference between writing the word with an open ta or a rounded ha; the meaning is determined by the context of the verse.