Recently we had a sister give a homily at Mass on vocations and a collection for retired religious. I thought that only priests and deacons can give homilies and the others are forbidden.
--Huffed in Houston
Yes, only the ordained may give homilies. Lay people and religious (sisters, brothers, monks, and nuns) may give "reflections." It may only be semantics, but it's like a presidential address: only the president may give one, others just give speeches in the name of the president.
And yes, a lay person or other person may be designated to give a reflection by the bishop or the pastor. Usually for the retired religious collection, which is done around the country, the bishops give permission for this reflection after the gospel or after communion.