①If trees are felled, they are cut down.【v.砍伐，砍倒(树木)】
②If you fell someone, you knock them down, for example in a fight.【v.击倒;打倒】
①Badly infected trees should be felled and burned.
②A blow on the forehead which felled him to the ground.
关于“砍伐”，这里再补充一个短语：chop down 【If you chop down a tree, you cut through its trunk with an axe so that it falls to the ground.】
Sometimes they have to chop down a tree for firewood.
这里再顺便补充一个关于“fell”的短语：in/at one fell swoop 一下子; 一举 【If something is done in one fell swoop or at one fell swoop, it is done on a single occasion or by a single action.】
In one fell swoop the bank wiped away the tentative benefits of this policy.
[scode type="share"]tag along
If someone goes somewhere and you tag along, you go with them, especially when they have not asked you to.
①I let him tag along because he had not been too well recently...
②She seems quite happy to tag along with them.
《经济学人》一篇关于日本奥林匹克的文章 Olympic gory 也出现了这个表达：