Short answer
A surah is a chapter of the Quran; there are 114 of them. An ayah is a verse within a surah; the word literally means "sign" or "miracle". So "Surah al-Baqarah, ayah 255" means chapter 2, verse 255 (Ayat al-Kursi). The Quran is also split into 30 juz for daily reading.
This is a factual matter. In the Hanafi school, reciting one ayah, even a short one, fulfils the fard of recitation in salah, and al-Fatiha plus a surah or three short ayat fulfils the wajib.
The four schools agree on this.
Explanation
Surah (plural suwar): the scholars give two origins for the word: a city wall or fence, since each surah is a section enclosed on its own, or a rank or high place, since each surah raises the reader. In English it is usually translated as "chapter". The Quran uses the word itself when it challenges people to produce "a surah like it" (2:23). The shortest surah, al-Kawthar, has three ayat; the longest, al-Baqarah, has 286.
Ayah (plural ayat): its root meaning is a sign. The same word is used for the signs of Allah in nature, the miracles of the prophets and the verses of the Quran, since each verse is a sign pointing to Allah. In English it is usually called a verse.
Other divisions:
- Juz (para in Urdu): one of 30 roughly equal parts. See the 30 juz.
- Hizb: half a juz, 60 in all.
- Ruku: a section marked in the margin of South Asian mushafs, a natural paragraph.
- Manzil: one of seven parts for reading the whole Quran in a week.
References are written surah:ayah, so 2:255 is Surah 2, Ayah 255. AmalKit uses this format throughout. Browse the surah list, or see how many verses are in the Quran.
The evidence
Quran, Surah Al-Baqara 2:23
وَإِن كُنتُمْ فِى رَيْبٍۢ مِّمَّا نَزَّلْنَا عَلَىٰ عَبْدِنَا فَأْتُوا۟ بِسُورَةٍۢ مِّن مِّثْلِهِۦ وَٱدْعُوا۟ شُهَدَآءَكُم مِّن دُونِ ٱللَّهِ إِن كُنتُمْ صَٰدِقِينَ ﴿٢٣﴾
And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful.
The Quran uses the word surah for its own chapters.
Where the ruling is recorded
- al-Hidaya, Kitab al-Salah, chapter on the description of prayer. The fard amount of recitation is one ayah per Abu Hanifa.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.