in his view it is analogous to sūr, the word for a wall, and therefore spelled without a hamzah.

Another explanation is that a sūrah received its name because it is cut off from the rest of the Qur’an, just as the Arabs call whatever remains in a vessel suʾr and speak of asār al-nās, “people’s leavings.” On that basis the original form would have been suʾrah, with a hamzah; the word was then lightened by replacing the hamzah with a wāw because of the preceding ḍamma.

A third opinion is that the term was chosen to denote completeness and perfection, for the Arabs describe a fully developed she-camel as a sūrah. The plural of sūrah is suwar, with the wāw pronounced short. A poet has said:
Dark of the eye sockets, they do not recite the suwar.
It may also be pluralised as sūrāt or suwarāt.

An āyah, by contrast, is a “sign,” meaning a marker that signals the break between the discourse before it and what follows; it stands apart from its sister verses, distinct and self-contained. The Arabs say, “Between me and so-and-so there is an āyah,” i.e., a sign; and the Most High says, “Indeed, the sign of his sovereignty…” (Q 2:248).

Al-Nābighah composed:
I traced her signs and recognised them—
Six full years, and now this makes the seventh.

Others hold that it is called an āyah because it is a cluster of Qur’anic letters, a discrete portion of the Revelation, just as one says, “The people set out in their āyāt,” meaning in their groups. Burj ibn Mushir al-Ṭāʾī said:
We marched out from the twin passes—no tribe like ours—
In our āyāt we drive the milch-camels and their calves.

A further view is that it is so named because it is a marvel that human beings are incapable of reproducing.

The grammarians have also differed over the word’s original form. Sībawayh held that it was ayayah, on the pattern faʿalah, like akamah (“hillock”) and shajarah (“tree”); when the yāʾ became mobile and was preceded by a fatḥah, it changed to an alif, yielding āyah, with a hamzah followed by an extended vowel. Al-Kisāʾī maintained that its root was āyiyah, on the pattern fāʿilah, like āminah (“secure”); the yāʾ was turned into an alif because it moved and was preceded by a fatḥah, after which it was dropped to avoid confusion with the plural. Al-Farrāʾ argued that the original was ayyayah, with the first yāʾ doubled; the doubling was disliked, so it was converted to an alif, resulting in āyah. Its plurals are āy, āyāt, and āyāʾ.

Abū Zayd recited:
Time has left of its āyāʾ nothing
But the cooking-stone tripods and the ashy hearths.