or - Salla 'Llahu 'alayhi wa sallam - This means "May Allah's peace and blessings be upon him" and it should be said after referring to Muhammad or other prophets. Sometimes abbreviated at "s.a.a.w.s." or "saaws"

 or 'Alayh is'Salam - This means "Peace be upon him" and it should be said after referring to prophets and angels.  Sometimes abbreviated as "PBUH".  

- , '  Radiya 'Llahu 'anhu - This means "May Allah be pleased with him" and should be said after referring to a male companion.

, ''- Radiya 'Llahu 'anha - This means "May Allah be pleased with her" and should be said after referring to a female companion.

Radiya 'Llahu 'anhuma - This means "May Allah be pleased with them" and should be said after referring to two companions.

Radiya 'Llahu 'anhum - This means "May Allah be pleased with them" and should be said after referring to more than two companions.

  Rahimahu 'Llah - (say rah-hee muh hoo-lah). This means "May Allah have mercy on him" and should be said after referring to a past scholar or righteous muslim.