Segments in Words

I am having trouble figuring out some segments and how they apply to numbers of letters. I am understanding words having more letters than segments, but not more segments than letters. For example, is there a word with 3 letters and 4 segments?

an individual speech sound. i have been trying some out and think i may have figured it out. for example:

at has two segmets - ae t
math has three segments - m ae (~) (theta)

would spy be an example of a word with four segmets, since phonetically it is s p a i?