IPA: //ˈspɛʃəlaɪz//
KK: /ˈspɛʃəˌlaɪz/
To focus on a particular area of study or work, becoming an expert in that field.
She decided to specialise in marine biology during her studies.
Past: specialised
Past Participle: specialised
Specialise → It is formed from "special" (from Latin "specialis", meaning particular or individual) and "-ise" (a suffix used to form verbs indicating the process of becoming or causing to be). The word "specialise" means to make or become specialized in a particular area or field.
Think of becoming more 'particular' ('special') in your skills or knowledge when you 'make' or 'cause' that focus ('-ise').