n
1 [U] reinforcing or being reinforced 加固; 加强; 增援.
2 reinforcements [pl] extra soldiers, ships, tanks, etc sent to reinforce armed forces, etc 用以增援武装力量等的士兵、舰船、坦克等; 援军.

n
reinforcements [plural]
more soldiers, police etc who are sent to a battle, fight etc to make their group stronger
　The police called for reinforcements .
positive/negative reinforcement
positive reinforcement is when you give someone praise or rewards for their behaviour or work, so they want to continue doing well. Negative reinforcement is when you give someone punishments or criticism when their behaviour or work is bad, so that they want to improve to avoid punishments again
　We need to give students plenty of positive reinforcement .
[U]
the act of making something stronger
　The bridge needs some structural reinforcement.