Happy. This word originally described somebody who benefited from chance (náhodné) events, and that's where the link with being lucky comes from. Of course, sombody who is lucky (má šťastie) is almost certainly also happy (je šťastný, veselý), but there are other meanings of "happy". Somebody who is slightly drunk can be called "happy" (or "merry"), but more important is the combination "happy with something" (So far the steelmakers are happy with their mechanical assistant.)

The normal translation of this is not "šťastný" or "veselý", but "spokojný", because the translation must express the same level of positive feeling. The dictionary translation of "spokojný" may be "satisfied", but in English that means somebody in a position of power who sets a certain standard, and who is then happy with the performance of people who come up to that standard, like when a teacher is satisfied with a student's work.