RadhiAllahu'anhu (Arabic: رضي الله عنه raḍiya 'llāhu ʿan-hu) is an Arabic phrase meaning, "Allah is pleased with him." This phrase is usually uttered after a Companion's name. There are grammatical variations used after the names of female companions or when more than one person is mentioned at the same time. For females, it is RadhiAllahu 'anha رضي الله عنها and in the plural, RadhiAllahu 'anh'um رضي الله عنهم.
References
Radhiallahu 'anhu Wikipedia(Text) CC BY-SA