Not to be rude or anything, but i believe its 'assembly'.
The terms are used interchangeably. Basically, it doesn't matter:
Note that, in normal professional usage, the term assembler is often used ambiguously: It is frequently used to refer to an assembly language itself, rather than to the assembler utility. Thus: "CP/CMS was written in S/360 assembler" as opposed to "ASM-H was a widely-used S/370 assembler."
http://en.wikipedia.org/wiki/Assembly_language#Assembler