pair自身可以是單數(shù)或者復(fù)數(shù).但是pair of 后面的名詞必是復(fù)數(shù)：a pair of shoes.
就是一把鉗子也是：a pair of pliers；
一條黑褲子：a pair of black trousers.
pair后面直接跟名詞組成詞組時,要根據(jù)具體情況來定.如果是定語性詞組,根據(jù)規(guī)則名詞用單數(shù)：
Pair Card Game
The system is modeled by the Hartree-Fock description of a pair electron interaction.
如果是名詞性詞組,則單、復(fù)數(shù)要根據(jù)句子的重點(diǎn)來定：
The player places a base pair card from his hand into the sequence.
In case when a winning combination or a pair cards are drawn,these cards will be held automatically.
Lone pair electrons have a stronger repulsion than bonding pair electrons.