The Spanish verb 'envejecer' (to grow old) is built from three main components that come from Latin roots. The base word is 'viejo' (old), which evolved from the Latin 'vetus' (old) through a diminutive form 'vetulus' (rather old) that became 'veclus' in Vulgar Latin. The prefix 'en-' comes from the Latin 'in-' meaning 'in, into'. The suffix '-ecer' derives from the Latin inchoative suffix '-escere', which was used to form verbs indicating a process of becoming or entering into a state.

When these elements combined, they created 'envejecer', literally meaning 'to become old' or 'to grow old'. The structure follows a common pattern in Spanish where 'en-' + [adjective] + '-ecer' forms a verb meaning 'to become [adjective]'.

The most obvious related Spanish word is 'viejo' meaning 'old', which is both simpler and more common than 'envejecer'. This adjective is the base word from which 'envejecer' is formed. You can think of 'envejecer' as simply meaning 'to become viejo'.

This pattern is similar to other Spanish verbs like 'enrojecer' (to redden, from 'rojo'), 'entristecer' (to sadden, from 'triste'), and 'enriquecer' (to enrich, from 'rico').

While English doesn't have any common words directly related to 'envejecer', we do have some scholarly or technical terms that share the Latin root 'vetus' (old). These include 'veteran' (someone with long experience), 'inveterate' (having a particular habit, behavior or interest that is long-established and unlikely to change), and 'veterinary' (originally referring to animals of working age).

Understanding this connection can help remember that 'envejecer' relates to the concept of age and becoming old, just as a 'veteran' is someone who has aged or grown experienced in their field.