Answered by: Maulana Tahsin Alam
Assalamu Alaikum Wa Rahmatullah
I would like to know quite clearly what Arabic words are used for Mahr which is considered to be prompt and for a Mahr which is to be deferred, along with some brief explanation of those words.
In the name of Allah, the Beneficent, the Merciful
‘Mahr,’ ‘ṣadāq’ or ‘ṣidāq’ are the Arabic terms for dowry. There are two types of Mahar:
1. Mahar Muʿajjal (with a ʿayn): The giving of a partial sum of the dowry to the wife before the marriage is consummated. This is a recommended practice due to the narration; Nabi SAW prevented Ali RA from consummating the marriage with his daughter (Fāṭima RA) until he gave her something before.
2. Mahar Mu’ajjal (with a hamza): The total payment of dowry, to be given to the wife, whose payment was deferred to a later date.
Only Allah Ta’ala knows best
Written by Maulana Tahsin Alam
Checked and approved by Ustadha Sabrina al-Faarsiyyah
Darul Ifta Birmingham
 Mulla ʿAli al-Qāri, Mirqāt al-Mafātīḥ (Pakistan: Maktabah Rashediyah, n.d.) volume 6 pg. 327.
This answer was collected from DarulIftaBirmingham.co.uk, which is run under the supervision of Mufti Mohammed Tosir Miah from the United Kingdom.