Matheteuo (μαθητεύω) means to make a disciple, to become a disciple, or to teach. It appears 4 times in the New Testament. Its most important occurrence is Matthew 28:19 — the Great Commission: 'Go and make disciples [matheteusate] of all nations.' This is the central command of the risen Christ to His church.
Matthew 28:19 is the theological fulcrum of matheteuo. In Greek, 'go' is a participle ('going'), while 'make disciples' is the main imperative — the core command. Baptizing and teaching are the two participles that describe how disciple-making happens. The Great Commission is not primarily about going but about making disciples through the twin practices of baptism (initiation) and teaching (formation). Matthew 13:52 uses matheteuo for a 'scribe instructed [matheteutheis] in the kingdom of heaven' — one who brings out of his treasure new and old. Acts 14:21 records Paul and Barnabas 'making many disciples' — matheteusantes — in the cities of the first missionary journey.