Sentence:  In this chapter we study the problem of classifying the finite-dimensional simple Lie algebras over an arbitrary field of <WSD>characteristic</WSD> 0. 
Meaning of the word marked with <WSD> tags:  For a given field or ring, a natural number that is either the smallest positive number "n" such that "n" instances of the multiplicative identity (1) summed together yield the additive identity (0) or, if no such number exists, the number 0.