INFIXES STANDING IN

You've familiar with prefixes and suffixes, but a lesser-known "affix" is the infix, which involves the insertion of a sound into the middle of a word. These show up pretty rarely in English, but back in Proto-Indo-European, the sound -ne- was pretty frequently inserted before the last consonant of roots to create a present active verb. This was called a nasal infix, and it mostly passed into Latin, Lithuanian, Ancient Greek, Sanskrit, and various Slavic languages. You can see some great examples of this phenomenon in pairs of Latin-derived words:

• Confuse and confound 
• Impact and impinge
• Convict and convince

All of these come from Proto-Indo-European words that contained nasals in certain situations but not others. Sadly, this didn't happen much in the Germanic branch of the family, but there is one remnant of it in English: stood and stand, where the n was inserted for the present tense word stand but not the past tense word stood. I think that's pretty interesting.