The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and a modified Met (fMet) in prokaryotes. The most common start codon is AUG. The start codon is often preceded by a 5` untranslated region (5` UTR). In prokaryotes this includes the ribosome.....
Synonym for initiation codon ... The codon 5' AUG in mRNA, at which polypeptide synthesis is started. It is recognised by formylmethionyl tRNA in bacteria and by methionyl tRNA in eukaryotes. ... (18 Nov 1997) ... 
See initiation codon.
Type: Term Synonyms: initiating codon
AUG codon, specifying methionine, which is typically the codon that initiates translation
The codon (AUG) on a messenger RNA molecule where protein synthesis begins.