This essay examines the similarities and differences among three kinds of translations: 1) from one natural language to another, 2) from one formal (mathematical) language to another, and 3) from one biochemical "language" to another (DNA to proteins in living organisms). The first is the most difficult, but life depends on the accuracy of the third, and all of computer science depends on the accuraracy of the second. Item (1) involvs both syntax and semantics; item (2) is primarily a problem in matching syntactical rules; but item (3) previously thought to be pure syntax, is now recognized as having large context-dependent properties, more like natural languages than expected.