The Arabic word nazr نظر is often used for an offering, but in its strict theological meaning it expresses a vow. Khairit pl. of Khair, is used for ordinary acts of charity. Sadiqah صدقةalso expresses the same meaning. Niyaz نياز is an offering to a saint. Zakat زكوة, the legal alms.
[For an account of these offerings refer to the words.]
Based on Hughes, Dictionary of Islam