I am in the "yeah, just let everybody speak common" camp - even though I have different solutions for alignment languages, etc.

However, I see many potential upsides to this approach.

First, it solves the "problem" where there is one "face" of the party and everyone else dumps Charisma. Nope, if you can't speak the language, you don't add your modifier to the reaction roll (etc.).

Second, some PCs and NPCs can talk secretly - or THINK they are talking secretly.

Sounds like a fun idea. If used sparingly.

Common Tongue is absolutely an authentic thing. In the west for most of history it was called Latin.  Now it's English.  In other parts of the world it was Arabic, (Mandarin) Chinese, etc.

The part that isn't realistic is that peasants speak it. "Common Tongue" is the tool to differentiate the people who are educated to some degree from those who aren't at all.

To some degree, but it sometimes changes - if source of Common Tongue is strong enough larger area can start use it down to peasants - like Celtiberians and Gaul turned to vulgar Latin, lots of world turned to dialects of English and Spanish and so on.

Yeah, how common "Common" is has a lot to do with how your world is set up. If you had a long lasting continent-spanning empire like Rome in the region and it only collapsed/withdrew two hundred years ago... then "Common" is probably everywhere (vulgar being just another word for "common") though linguistic drift is definitely resulting in regional accents.

300-400 years out though there will have been enough drift that different regions will no longer be mutually understandable.

I base the timing off historical records indicating that up until the middle of the 7th Century there remained mutual understandably in Latin between speakers from even distant portions of the former empire (i.e. both could speak their native tongue and be mostly understood by the other), but that by the end of the 9th Century such mutual understandability was no longer possible (i.e. if both spoke their native tongues they could not understand each other... one or the other would need to learn the other's language to understand each other).

The point being... if you want there to be a "Common" in your world, make sure to set it up in a way to make it plausible. It's why I specifically included a global magitech empire that had ruled for about 500 years and which collapsed 200 years ago in my world. It's in the waning days of a mutually intelligible common language (lots of NPCs with accents if they aren't locals) so characters can mostly be understood by anyone, but accents and colloquialisms can be used to accentuate foreigners.

Plus, relatively recently fallen mighty empires also make good sources of ruins for adventurers to plunder without being so old as to be completely stripped of all valuables (especially given the massive population implosion that accompanied the empire's collapse).

Quote from: Chris24601 on November 12, 2020, 11:23:39 AM
Yeah, how common "Common" is has a lot to do with how your world is set up. If you had a long lasting continent-spanning empire like Rome in the region and it only collapsed/withdrew two hundred years ago... then "Common" is probably everywhere (vulgar being just another word for "common") though linguistic drift is definitely resulting in regional accents.

300-400 years out though there will have been enough drift that different regions will no longer be mutually understandable.

I base the timing off historical records indicating that up until the middle of the 7th Century there remained mutual understandably in Latin between speakers from even distant portions of the former empire (i.e. both could speak their native tongue and be mostly understood by the other), but that by the end of the 9th Century such mutual understandability was no longer possible (i.e. if both spoke their native tongues they could not understand each other... one or the other would need to learn the other's language to understand each other).

The point being... if you want there to be a "Common" in your world, make sure to set it up in a way to make it plausible. It's why I specifically included a global magitech empire that had ruled for about 500 years and which collapsed 200 years ago in my world. It's in the waning days of a mutually intelligible common language (lots of NPCs with accents if they aren't locals) so characters can mostly be understood by anyone, but accents and colloquialisms can be used to accentuate foreigners.

Plus, relatively recently fallen mighty empires also make good sources of ruins for adventurers to plunder without being so old as to be completely stripped of all valuables (especially given the massive population implosion that accompanied the empire's collapse).

Your numbers might work for humans in isolation, but if your game world includes integrated dwarves, elves, and gnomes as speakers of Common, then those times for language drift need to account for speakers that live for several centuries.

Quote from: HappyDaze on November 12, 2020, 12:25:00 PM
Your numbers might work for humans in isolation, but if your game world includes integrated dwarves, elves, and gnomes as speakers of Common, then those times for language drift need to account for speakers that live for several centuries.

My dwarves don't live any longer than humans do (and are relatively well integrated into human society as it is... humans with dwarven ancestry are more common than those with elvish ancestry) and elves and gnomes first arrived in this dimension at the same time the empire collapsed (the two were caused by the same Cataclysm) already speaking their own language. They didn't even start learning the common tongue until well after the empire had collapsed. All my other species either have lifespans either comparable to humans (beastmen are actually less overall, but reach maturity in 1-2 years so the overall 60 year lifespan isn't a big deal in terms of PCs) or are also relatively recent arrivals/creations (the golems were created in the heyday of the now fallen empire and have the classical version of the language, which I demonstrate in play via use of Received Pronunciation vs. Midwestern American for those speaking the local dialect).

In other settings, dwarves, elves and gnomes tend to have their own isolated cultures (i.e. minimal contact with humans vs. living among humans) with their own native languages (dwarven, elven, etc.) that they maintain. Dwarven, elven and gnomish communities also tend to be smaller than the human populations which further reduces the degree of contact between them and human commoners. That the demi-human species also speak human common is largely a game contrivance to allow the PCs to be able to easily communicate with each other.

As such, I'd say the timescales are about right because in just about any settings the humans are going to be the primary drivers in changes to the human common language without enough contact with elves or dwarves or gnomes to matter (if anything I'd expect most elves to need remedial courses in common every couple of centuries as it continues to drift while they and their native elven tongue remain more or less static).

Quote from: Chris24601 on November 12, 2020, 02:59:01 PM
In other settings, dwarves, elves and gnomes tend to

Your own setting is all yours, but "other settings" don't all share the tendencies you suggest. Eberron is but one example where your tendency does not apply at all.