An ayah linguistically is a sign or symbol. In regards to the signs of Allaah then they are of three types:
1) Aayaat Munazzalah
2) Aayaat Ufuqiyyah
3) Aayaat Nafsiyyah
The first, Aayaat Munazzalah, are the signs of Allaah that were revealed to the Messengers. They are what Allaah revealed to the Messengers and commanded that they convey to the people, such as the Qur’an, the Tawraat, the Injeel (Gospels of Jesus) and the scribes of Ibraheem. These Aayaat are UNCREATED as they are the speech of Allaah, The Most High.
The second type, Aayaat Ufuqiyyaah, are the visible signs present in the universe that attest to the presence of Allaah and His great ability and might. Examples of these Aayaat are the sun, moon, stars, heavens and earth as Allaah says:
“And from among His Signs are the night and the day, and the sun and the moon. Prostrate not to the sun nor to the moon, but prostrate to Allah Who created them, if you (really) worship Him.” [41:37]
“Verily! In the creation of the heavens and the earth, and in the alternation of night and day, there are indeed signs for men of understanding.” [3:190]
The third type, Aayaat Nafsiyyah are the innate signs. The signs present within one’s self that attest to Allaah’s amazing ability. He سبحانه وتعالى said:
“And also in your ownselves. Will you not then see?” [51:20]
“We will show them Our Signs in the universe, and in their ownselves, until it becomes manifest to them that this (the Quran) is the truth. Is it not sufficient in regard to your Lord that He is a Witness over all things?” [41:53]
The second and third type are created signs that one perceives in the universe and in the self that confirm the presence and ability of Allaah. The first type is in uncreated and confirm the fact that Allaah sends guidance for the slaves, through revelation to Messengers, in order that they worship Him, alone, in a manner that He legislated. The slave may perceive the signs in himself and in his surroundings and come to the realisation of the Almighty, but he will not find salvation unless he follows the guidance and revelation sent by Allaah.
والحمد لله و صلى الله وسلم على رسول الله