What spelling, grammar or semantics rules have been lost in your lifetime?

“Decimating” no longer means killing ten percent as the Romans did; now it is used to mean the killing of a majority, so it’s close to the opposite of its original meaning.

We were always supposed to put punctuation inside quotation marks; however, now it seems to be the user's choice of inside or outside. And I have to admit that most of the time when I’m using quotes, it seems more logical to me to place the punctuation outside of them.

Loose and lose might as well be the same word these days. Drives me up a damn wall.

That and "POV" doesn't mean what it used to mean anymore. Also drives me up a wall.

Australian English language is now largely Americanised, a process that started in the post-war era is now mostly complete.

• Terms such as 'gaol' have been widely replaced by 'jail'.
• 'Programme' is mostly replaced by 'program'.
• A 'car bonnet' is likely to be called a 'hood'.
• 'Play lunch' is mostly replaced with 'recess'.
• 'Pusher' is mostly called a 'pram'
• 'Lacker band' is now mostly just 'rubber band'.
• 'Boomer' no longer means kangaroo, but instead 'Old person.'

I'm not really bothered by it or anything, but it's been interesting to see it shift even over my lifetime.

Literally is still understood, it just gets misused.

Going in a bit of a different direction, emojis and things like /s are well understood now, which is an addition.

"begging the question". it's not the same as "bringing up a question", it means assuming your conclusion is true in the course of an argument

I suppose the word "boomer" has changed meaning very quickly. It rarely gets used anymore to refer to actual boomers (people born just after WW2) and instead now can refer either vaguely to anyone older than 30, or anyone with an antiquated/problematic notion of social norms.

From my perspective, literally being used for emphasis does not actually change its meaning, it’s simply hyperbole.

If you complain that you’ve been “waiting for hours”, even though it’s been 45 minutes, that doesn’t change the meaning of “hours”, you’re just exaggerating.

Hyperbole is a stylistic element; style is a completely different level of language than grammar/spelling/semantics (word meanings). As another example of style, ending a sentence with a preposition is grammatically correct but stylistically not recommended.

I miss double spaces after periods.

Presently used to mean "soon" or "in a bit" but now means "happening right now"

The meaning of bemused is similar to "befuddled", but it's more often used as if it means "amused"

It used to be a firm rule that you mustn't end a sentence in a proposition.

Pour one out for the Oxford Comma .

Let's eat Grandma

Commas save lives!

While not totally gone, German's genitive case (which is used to show ownership) is becoming less and less common. They have both the genetive case as well as their equivalent of " 's " - which is just "s," if you're wondering. Example:

Der Herr der Ringe.

The Lord of the Rings. It would normally be "die Ringe," but it becomes "der" in the genetive case.

Another transition in German is that the "formal you" is being used less and less frequently. I understand this is the case for a few other European languages as well.

“Casted”

The past-tense of cast is cast. “The fisherman cast their line into the river.” “The actor was cast in the leading role.”

Casted makes you sound like a child.

would of literally their

People using then instead of than. I never saw that 30 years ago.

Apple put the nail in the coffin for adverbs when "Think different" let illiterates think they were speaking correctly.

Ain't ain't a word.

It is now.

also i fear that "comfort" is losing the battle to "comfortability"

Not exactly what you're asking, but double spaces after ends of sentences.

Ending sentences with propositions, and getting them jumbled around. My work does it in their advertisements and i cry every time.

"See what classes you can register for." Or modifying it to be worse; "see what classes you can register for fast"

Pronouns getting weird, especially when and is added, like "for him and I" or "her and I's house".

Also excetera for etcetera and mischievious for mischievous

"Reticent" used to mean 'reluctance to speak', or, 'holding your tongue', but in the last decade I saw it being used more frequently as a straight up synonym for 'reluctance'. I wonder if people maybe think it's a more authoritative sounding word?

It's not a change of convenience or cultural drift, just a sign of people reading less and subconsciously trying to hide it, I think.

Unique coming to just mean unusual.

The one that bothers me most (heard a lot in the software dev world) is when people say process-eez instead of processes, even if it is technically a word now, like ain’t

I don't know if this fits the question, but in Brazil the "Portuguese-Language Orthographic Agreement of 1990" only started to take effect in 2009 (after I was born), in a transition state, and in 2015 it became official and obligatory.

The changes that I still fumble with are diacritics (e.g. "Idéia" -> "Ideia") and hyphens (e.g. "contra-regra" -> "contrarregra").

I was one of the first years to have the new spelling rules.
It used to be, that a letter appearing more than twice in direct sequence would be cut to just twice. But that was lifted and is now just how many it should normally be. Examples: Schifffahrt, Brennnessel, Seeelefant.

It used to be, that "dass" could also be spelt "daß", but the rules for "ss" and "ß" were made clearer and more concise.

They also changed the way words could be split at the end of a line. If there was a double consonant in-between the syllables that were to split, the first syllable would take both consonants but now they are split evenly.
immer is split im-mer and not imm-er
But ck makes an exception: knackig is kna-ckig instead of old knak-kig

In US usage, it used to be that a situation could be "fraught with" complications, or hidden meaning, or difficulty, but it had to be "fraught with" something.

These days, the British style of saying that the situation is simply "fraught" seems to be way more popular than before.

Efficiency at work i guess. Maybe some cunning linguist can explain.

Literally and Crescendo are my vocabulary pet peeves. Both have stupidly evolved to include definitions that mean the exact opposite of their true meanings.

Literally is annoying, but Crescendo is impossible. That is a specific musical term with an unalterable meaning. It means a gradual increase in volume, but it has come to mean a climax. Something will be described as "it rose to a crescendo," and that is simply wrong. Something can crescendo to a climax, but not the other way around. If you change it to mean the climax, you can't crescendo to a crescendo, s what's the word for gradually increasing the volume?

Besides, it's a musical term, and musicians will define musical terms, not illiterate civilians.

And if Literally can also mean "similar to," then what word can be used to literally mean Literally?

People no longer double-space after sentences.  No one cares that further compares metaphorical distance and farther compares physical distance.  Most people seem to think that joining two independent clauses with a comma (a comma splice) is just fine.  Things are now done on accident instead of by accident.  Compute used to be something you did; now, it's something you rent.  People seem to have given up on less being used for uncountable things and fewer for countable things.  Now they just use less for everything.  People these days are enamored 'by' something instead of with it (or of it, for our British friends).