Wait, so the most common plant life by weight isn't algae, then? What is it actually?

Factoid has two almost opposite meanings

1. an insignificant or trivial fact.

2. something fictitious or unsubstantiated that is presented as fact, devised especially to gain publicity and accepted because of constant repetition.

To my mind, the connotation of factoid is that it's not false, but it's too simplified or stripped of context to be wholly accurate.

Consider, "Did you know that squids have eyes as big as bicycle tires?" That's not completely made up (squid do have the largest eyes of any animal) but to make it strictly accurate you'd need to change "squid" to "giant squid", "have" to "can have", and "bicycle tire" to "child's bicycle tire".

Ah, the second definition isn't one I've ever seen used? A factoid may be used inappropriately to support an unrelated argument, ("the last pirates were seen in the 1800s, right as climate change started") but they're still _true_.

That's actually the original meaning. "Factoids... that is, facts which have no existence before appearing in a magazine or newspaper, creations which are not so much lies as a product to manipulate emotion in the Silent Majority."

The meaning has since mutated, and of course there's no reason we should be constrained to the original.

It's the original and etymologically, it makes more sense, since "-oid" means "resembling." "Humanoids" are not human, for instance. But of course appeals to etymology are not a good way to determine what a word means.

Interesting. Are there any other words in the English language with two contradicting definitions?

"Flammable" and "inflammable" mean the same thing. (Not quite what you were asking, but it's in the spirit of the question, I think).

"Literally" is often used for emphasis, even when something is figuratively but not literally true.

"Enjoin" means both to proscribe and to prescribe.

"Sanction" is similar; it's either a penalty for breaking a rule, or official approval of something.

"Dust" (as a verb) means both to clean dust off of something or to spread dust onto it.

"Fast" means fixed in one place or moving quickly.

"Oversight" means watching over something carefully, but also a mistake caused by a missed detail.

"Cleave" means both to cling/adhere and to split/sever.

"Hold up" can mean support or hinder.

This list can keep going. It's just the point that I got tired of finding more listicles to pull the best bits out of.

There are literally millions of them.

Some people object when a word means its opposite, but I could care less.

I can't sanction your response.

Lots!

https://en.wikipedia.org/wiki/Auto-antonym

So, uh, factoids collectively were the fake news of their day?

Why do you say that? I don't see how that follows from beat's comment...

The -oid suffix means "similar to" or "resembling."

For example: a humanoid is something resembling a human, but not a human.

So, traditionally, a factoid is something resembling, but not, a fact.

However, it has been misused for so long, it's now considered by many ok to use "factoid" to mean a trivial, related fact.

> considered by many

It's the first definition in the dictionary.

There is no "the" dictionary. And in most respected dictionaries, it isn't the first definition.

https://www.merriam-webster.com/dictionary/factoid

https://en.oxforddictionaries.com/definition/factoid

Some dictionaries order senses by age and others by usage (which may be somehow measured or may just be up to the instincts of the editors), so this isn't a useful metric without knowing the standard of the dictionary we are talking about.

Which dictionary do you mean? Do you mean that highly inaccurate one that you get when typing a word into Google.com?