Second string and Younger

Second string noun - A squad of players that are available either individually or as a team to relieve or replace the players who started the game.

Younger and second string are semantically related. In some cases you can use "Younger" instead an adjective phrase "Second string".

Younger adjective - Used of the younger of two persons of the same name especially used to distinguish a son from his father.

Second string and younger are semantically related. Sometimes you can replace phrase "Second string" with "Younger", this terms are similar.