From Pluralpedia, the collaborative plurality dictionary
mendabased (adj.)
Mendabased flag.png
The flag is a simple flag, but everything has meaning. The dark orange represents deceit, which could be a cause of mendabased headmates. The yellow represents dishonesty, cowardice, and deceit, which could all be menda in nature. Finally, the serpent represents dishonesty.
Applies toheadmates
CoinerEdward "Edwie" Nygma of the Volatile Lovers Order subsystem, Peter Parker of the Turtles All The Way Down Collective sidesystem, and Sir Beau Mazurkieicz Esq. of the Ex Animo Ex Nihilo Collective sidesystem, all of The Halcyonic Storms of Anemoia astropoly polypex Deathstarkille
Origincomes from Latin Medacium, meaning "a lie, fib, or falsehood"

A headmate that was given false information about themselves, on purpose or otherwise, which eventually became a part of them or a truth to them.

Mendabased headmates are any headmates that have any information about themselves that wasn't necessarily true when they first formed, whether they be a fictive, factive, or what have you.

Any information can be considered false, it just depends on what a headmate considers to be false information that became a part of themselves. An example given by the coiner is a headmate of theirs, Freddy Freeman. He is 14 years old, but due to false information given to him by another system, he believed he was 11 years old, and that information became a part of him, thereby making him mendabased.

Being mendabased isn't permanent; if a headmate eventually learned of the false information and decided to somehow remove it, through means such as affirmations, memory altering, or anything else, they could then become a headmate without any menda information.

As mentioned above, the information doesn't have to be a lie, or even something designed to hurt a headmate. The information given could have been a mistake, or a genuine misunderstanding, but either way, for the headmate in question, the information just simply isn't true. That doesn't mean, however, that all menda information is accidental.

In some instances, one might give a headmate menda information in order to control them, gaslight them, gatekeep them, or otherwise change them in any other way. This can be done for any number of reasons, but again, mendabased isn't permanent, and one can go back to being without the menda information.