ob
The word is obscure.
ob which means toward, against, in the way
To put an obstacle in the way
The prefix od- otherwise known as ob- means toward, against, or completely.
The prefix for "oblivious" is "ob-".
The prefix of "oblige" is "ob-".
The prefix of "obtrusive" is "ob-".
The prefix of "obsess" is "ob-".
the prefix ob means against something e.g objection, obstacle, obstruction
Yes, "obstruct" has a prefix "ob-" and a suffix "-ct." The prefix "ob-" means against or in opposition, while the suffix "-ct" is a verb-forming suffix in this case.
The true opposite of prefix is no prefix.But, as a prefix means something added at the start of a word. the generally understood opposite is suffix - which is something added to the end of a word.