If you are asking about military, cadete = cadet. Talking about sports, football for example in Spain there are different categories by age: Senior Absoluto Sub-19 Juvenil de tercer año Sub-18 y Sub-17 Juvenil Sub-16 y Sub-15 Cadete Sub-14 y Sub-13 Infantil Sub-12 y Sub-11 Alevín Sub-10 y Sub-9 Benjamín Sub-8 y Sub-7 Pre-Benjamín So, if you are 16 and you play football you’ll be “cadete” . In UK it should be young player or Under 16.

un cadete - a cadet cadetes - cadets