condition
1.in good condition, in perfect condition, in firstclass condition, in bad condition, in poor condition等表达方式里都没有a。in a filthy condition, in a horrible condition, in a serious condition等表达方式里都有a。似乎在笼统地说“好”或“坏”的时候不用a，但在说明“怎样的”的时候用a。
2.under（或in）favourable conditions, under（或in）unfavourable conditions, under（或in）difficult conditions, under（或in） present conditions, under（或in）existing conditions等表达方式里都用复数形式conditions。这里的conditions指“环境”，在1里所说的condition指“情况”。“环境”会影响“情况”。例如：The oranges, which are now in good condition, may soon rot under present conditions.
3.I will allow you to use my library on this condition里用on。
4.I will allow you to use my library on condition of your not taking any book away里在condition前面习惯没有the。
5.on condition that...（把…做条件）在condition前面偶尔有the。但假使condition前面加上形容词，必须有the。例如：on the express condition that...
6.下面每组里的各句意思相同：
- He agrees to this, on (the) condition that she stays in town.
He agrees to this, on (the) condition that she shall stay in town.
He agrees to this, on (the) condition that she should stay in town.
He agrees to this,on(the) condition that she stay(虚拟现在式) in town. - He agreed to this, on (the) condition that she stayed in town.
He agreed to this, on (the) condition that she should stay in town.
He agreed to this,on(the)condition that she stay(虚拟现在式) in town.
