2 different concepts of 'round' are in the rules. One that ends when everyone has taken a turn and one that lasts from a character's turn to the start of their next turn. The concepts are not new, we can see them from previous editions.
In the 3.5 rules, it says:
A round can be a segment of game time starting with the first character to act and ending with the last, but it usually means a span of time from one round to the same initiative count in the next round. Effects that last a certain number of rounds end just before the same initiative count that they began on
In the 5th edition Basic Rules, only the first one is defined while the 2nd one is simply implied by the 'Reaction' and 'Ready' action. This can lead to some confusion. For example, if you apply the first definition of 'round' to the 'Ready' action, it doesn't make a lot of sense for characters acting later the round, their 'Ready' action would do nothing.
Another example is when you take a reaction, you can't take another one until the start of your next turn while 'Ready' action also reminds you that only one reaction per round is allowed. If we use the 2nd definition of round for this, both sentences would have the same meaning. But the problem is that only the first type of round is defined in the rules, which would apply 2 different restrictions to 'Reaction'.
In conclusion, the wording of the rule is not clear and can create quite a few confusions, it may not affect us since we are used to the 2 differents types of 'round' . For new players, it can be difficult to understand. I hope the rules in the PHB are better written, I don't want 5th edition to be another edition plagued by errata.
Yes, there are quite a few rules that are poorly worded in the basic rules such as the interaction between normal vision and darkness. And from I saw from the recent excerpts, it seems PHB hasn't fix those problems, I could be wrong and I wish I am.
Bahamutspower wrote:
An hour can refer to the span of time from one full hour to the next (that is, from 2:01 to 3:00), or it can refer to any span of 60 minutes (such as from 2:51 to 3:51).
This is not a problem with the rules, this is an ambiguity of the way time is dealt with in the English language; any unit of time can be used to refer to a specific labeled segment of that length, or of a timed period equal to its length.
ankiyavon wrote:
The Ready rules' mention of reactions is iffy. I would go with the reaction rules instead.
Don't worry about the 3.5 definition of a round. They've intentionally moved away from giving spells durations in rounds because of how confusing it was to have two definitions for one term. Spells now have durations in minutes and hours and (AFAIK) never rounds.
ankiyavon wrote:
Shroom-Mage wrote:
I agree that the wording is unsatisfactory.
On the one hand there are "clock" rounds, as defined in Chapter 9, which run once though the initiative order and end when the last creature has had a turn; and there are "durational" rounds which run from any creature's turn to the start (or end) of the same creature's next turn.
The wording for "Reaction" is explicit - it's once per "durational" round, so that's not a problem. Spells that have a duration of 1 round use the "durational" round too. For example, Command has a duration of 1 round and takes effect on the target's next turn (whenever that is); Guiding Bolt has a duration of 1 round and takes affect before the end of your next turn; Shield has a duration of 1 round and lasts until the start of your next turn; and so on.
It's really only the "Ready" rule that is a problem. Does a readied action expire at the end of the clock round, or is it durational? There are two schools of thought.
The PHB won't answer the question because the Basic PDF was extracted from it verbatim, after the PHB went to the printers. The wording will be identical to what we already have.
MightyZehir wrote:
Emerikol. wrote:
I think they should have used to different terms. Plenty of other games do (IIRC, Hero uses round for one and turn for the other).
It would have been a simple way to clarify. Unfortunately, that train has sailed. 
It's certainly not the end of the world. I imagine that in most situations you can determine which version they mean from context.
Perhaps we could use the term "combat round" to mean "the process of working through the initiative order once" and just use "1 round" to mean the time between a creature's turn in one combat round and the same creature's turn in the next combat round.
There's a problem introduced by Thief's Reflexes, though, which grants a thief two turns in the same round.
If a thief uses his first turn to do something with a duration that ends "at the beginning of your next turn", then RAW would dictate that it ends on his second turn the same combat round, not on his turn in the following combat round. Common sense would no doubt prevail. But what about reactions? Can the thief have one reaction between his two turns, then another reaction after his second turn, both in the same combat round?
BoldItalic wrote:
Rob Hamilton @chimerasame @mikemearls Can a low-init character ready an action, then take that action if legit triggered by a high-init character in the next round?