1. Compiler: [Computer Science] A program that translates another program written in a high-level language into machine language so that it can be executed.
2. Assembler: [Computer Science] A program that produces executable machine code from symbolic assembly language.
(source:dictionary.com)
3. Semantic: (i)Of or relating to meaning, especially meaning in language. (dictionary.com). (ii) [comp.sci] The meaning attached to words or symbols (wordsworth dict. of sci and technology)
Semantic analysis: In computer science, semantic analysis is a pass by a compiler that adds semantical information to the parse tree and performs certain checks based on this information. It follows the parsing phase, in which the parse tree is generated, and precedes the code generation phase, in which executable code is generated. Typical examples of semantical information that is added and checked is typing information (type checking) and the binding of variables and function names to their definitions (object binding). Sometimes also some early code optimization is done in this phase.
(src: Wikipedia)
4. Lexical: Of or relating to the vocabulary, words, or morphemes of a language (dictionary.com)
Lexical analysis: (Or "linear analysis", "scanning") The first stage of processing a language. The stream of characters making up the source program or other input is read one at a time and grouped into lexemes (or "tokens") - word-like pieces such as keywords, identifiers, literals and punctutation. The lexemes are then passed to the parser.
(hyperdictionary.com)
5. Code Generation: the generation/production of the symbolic arrangement of data or instructions in a computer program or the set of such instructions.
sorry, wasnt able to find anything on 'assembly language set'.