For alphabetization purposes, iso- and neo- are considered part of the name, and alphabetized. Sec- and tert- are not considered an alphabetizable part of the name.
(In the following images, the R- represents any carbon structure.)
Iso-
Iso- can be used for substituents that branch at the second-last carbon and end with two methyls. An isobutyl has four carbons total:
Isobutyl
Sec-
Sec- can be used for substituents that branch at the first carbon .
Neo-
Neo- refers to a substituent whose second-to-last carbon of the chain is trisubstituted (has three methyl groups attached to it). A neo-pentyl has five carbons total.
Neopentyl
Tert-
Tert- is short for tertiary and refers to a substituent whose first carbon has three other carbon groups attached to it.
By definition, a primary carbon is one which is attached to one other carbon atom, a secondary carbon is one which is attached to two, a tertiary carbon is attached to three, and a quaternary carbon is attached to four other carbon atoms; these are often abbreviated as 1o, 2o, 3o and 4o carbons.
plz rate it if satisfied.