Sentence:  Let n be a positive integer and let V be the space of all n times continuously differentiable <WSD>functions</WSD> f on the real line which satisfy the differential equation * * f where * * f are some fixed constants . 
Meaning of the word marked with <WSD> tags:  (mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)