say command says wrong text (for some voices)

Solution 1:

These voices come from Nuance. If you try their Vocalizer Demo you can hear that "seq" is replaced by "the following" there as well.

This appears to be similar to Nuance's recognition of "homographic abbreviations", where Nuance will attempt to convert an abbreviation into the full word.

I have noticed that there are other words that are interpreted

• e.g. "for example"
• sat. "Saturday"
• mar. "March"

Solution 2:

Obviously, what’s spoken is not what you expected to be spoken. I’m not sure I would call it “wrong”, though. “seq” is a fairly obscure dictionary entry in the first place, and “the following” is one possible expansion of this abbreviation (although I think “and the following” would be better), e.g. in literature references:

Knuth, Art of Computer Programming Vol 1, pp 329 seq.