What is the meaning of ا?

Although usually considered to be the first letter of the Arabic alphabet, the small hamza (ء (ʔ)) that sits on top of أ (ʔ) is really the first letter of the Arabic alphabet, and the tall column is its bearer. This entry only deals with the lower part, the bearer, which is called أَلِف (ʔalif) and, without the hamza, is used to lengthen a preceding a.

The first letter in traditional abjad order, which is used in place of numerals for list numbering (abjad numerals). It is followed by ب (b).

The first letter of the Balti alphabet, written in the Perso-Arabic script

The first letter of the Burushaski alphabet, written in the Perso-Arabic script

they; third-person plural pronoun

The first letter of the Khowar abjad.

The first letter of the Kyrgyz in Arabic Script. It represents the Cyrillic letter А

Alternative spelling of ـها when it is not pronounced as “-ha”

The first letter of the Xiao'erjing abjad.

The first letter of the Gujarati abjad

The first letter of the traditional alphabet chart of Kashmiri.

The first letter of the Kazakh in Arabic Script. It represents the Cyrillic letter А or Ә.

The first letter of the Malay alphabet, written in the Arabic script.

The first letter of the Pashto alphabet.

The first letter of the Perso-Arabic alphabet. Its name is اَلِف (alef).

from, since

The first letter of the Punjabi written in the Shahmukhi script.

The first letter of the Sindhi abjad.

The first letter of the Urdu abjad.

A negating prefix. non-, un-, a-, an-, etc.

The first letter of the Yorùbá alphabet in the Ajami Script.

Source: wiktionary.org