There are a few changes - some minor, some more significant - in the latest printing of the PHB that are not noted in the 2018 errata PDF:
- Action Surge
- Awakened Mind
- Climbing, Swimming and Crawling rules
The fighter's Action Surge feature previously read (PHB, p. 72; emphasis mine):
On your turn, you can take one additional action on top of your regular action and a possible bonus action.
The bolded phrase was removed in the latest printing as of November 2018, and the Action Surge feature description now reads:
Starting at 2nd level, you can push yourself beyond your normal limits for a moment. On your turn, you can take one additional action.
This change is confirmed in the January 2019 edition of the Sage Advice Compendium:
Does the fighter’s Action Surge feature let you take an extra bonus action, in addition to an extra action?
Action Surge gives you an extra action, not an extra bonus action. (Recent printings of the Player’s Handbook no longer include the wording that provoked this question.)
Rules designer Jeremy Crawford also confirmed the change in the November 27, 2018 edition of Dragon+ (in which he discussed the errata), describing it as "unhelpful helper text" that caused people to interpret it as saying the opposite of what it actually meant. (Thanks to CTWind's answer here for the timestamped link!)
In previous printings of the PHB, the Great Old One warlock's Awakened Mind feature read (PHB, p. 110; emphasis mine):
You can communicate telepathically with any creature you can see within 30 feet of you.
However, the description of the Awakened Mind feature in the latest printing of the PHB reads (emphasis mine):
You can telepathically speak to any creature you can see within 30 feet of you.
Of note, this change makes it so that Awakened Mind's telepathy is more clearly one-way rather than two-way. This matches the rules intent as indicated in one of the earliest versions of the Sage Advice Compendium in 2015 (v1.01), and still listed there in the 2019 Sage Advice Compendium (v2.3):
Does the warlock’s Awakened Mind feature allow two-way telepathic communication?
The feature is intended to provide one-way communication. The warlock can use the feature to speak telepathically to a creature, but the feature doesn’t give that creature the ability to telepathically reply. In contrast, the telepathy ability that some monsters have (MM, 9) does make two-way communication possible.
The fact that the wording of the feature was changed from previous printings of the PHB, however, is not mentioned in the errata PDF or in the Sage Advice Compendium entry.
Climbing, Swimming and Crawling rules
The rules on Climbing, Swimming, and Crawling (PHB, p. 162) originally said:
While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing or swimming speed. At the DM's option, [...]
As this question by Daniel Zastoupil and its answers note, there was technically some ambiguity about whether this meant having a climb/swim speed was sufficient to ignore the extra movement costs, or whether the creature needed to use those speeds in order to not have to spend extra movement.
However, as of November 2018, the rules on Climbing, Swimming, and Crawling now state (emphasis mine):
Each foot of movement costs 1 extra foot (2 extra feet in difficult terrain) when you’re climbing, swimming, or crawling. You ignore this extra cost if you have a climbing speed and use it to climb or a swimming speed and use it to swim. At the DM’s option, [...]
This change to the PHB (and basic rules) is not mentioned in the errata.
The first sentence of the clone spell description (PHB, p. 222) originally read (emphasis mine):
This spell grows an inert duplicate of a living creature as a safeguard against death.
However, as of November 2018, the clone description now begins (emphasis mine):
This spell grows an inert duplicate of a living, Medium creature as a safeguard against death.
The fact that it simply says "Medium" instead of "Medium or smaller" means that it's now impossible to use the spell to clone any Small creature. This seems like an oversight (presumably the intent was to prevent cloning Large or bigger monsters with it), in which case a future errata may fix it accordingly.
This added size specification is not mentioned in the errata PDF.
There are 2 "non-changes" in the 2018 PHB errata that actually misleadingly seemed like a change at first:
- Deflect Missiles initially looked like it was changed (but it
wasn't); the errata document notes a different phrasing from before
but doesn't mark the supposed change as "[NEW]". However, the listed
phrasing is slightly inaccurate, leading to some confusion.
- Martial Adept also seemed like it changed (but it didn't
actually), only because many people misinterpreted an earlier
errata's paraphrasing of the change - or because the errata's
paraphrasing itself was misleading/inaccurate.
The last sentence of the monk's Deflect Missiles feature (PHB, p. 78) originally read:
You make this attack with proficiency, regardless of your weapon proficiencies, and the missile counts as a monk weapon for the attack.
The first PHB errata in 2015 summarized the change as follows (and the same summary remained unchanged through the 2017 errata):
Deflect Missiles (p. 78). The range of the monk’s ranged attack is 20/60 feet.
Instead of summarizing the change, the 2018 errata states the exact phrasing to be used - which oddly leaves out the information about the range of this attack that was added in previous errata:
Deflect Missiles (p. 78). The final sentence now ends as follows: “... regardless of your weapon proficiencies, and the missile counts as a monk weapon for the attack.”
This leaves out the information about range added in previous errata.
However, the last sentence of the monk's Deflect Missiles feature actually currently reads (emphasis mine):
You make this attack with proficiency, regardless of your weapon proficiencies, and the missile counts as a monk weapon for the attack, which has a normal range of 20 feet and a long range of 60 feet.
This wording is seemingly unchanged from when the range of the attack was initially added in the 2015 errata. It appears that the 2018 errata simply incorrectly quotes the end of the final sentence of the feature, matching the version in the first printing of the PHB rather than the latest printing.
The Martial Adept feat (PHB, p. 168) originally read, in the first printing of the PHB:
If you already have superiority dice, you gain one more; otherwise, you have one superiority die, which is a d6.
(Thanks to Mindwin's question here for the quote.)
Naturally, people interpreted this as meaning that the feat was better for Battle Master fighters (PHB, p. 73-74) than for others, since Battle Masters gained an extra superiority die of the same size as their existing superiority dice (all of which scale with their level).
The very first errata to the PHB (in 2015) summarized its change to the feat as follows (and this summary remained unchanged through the 2017 errata):
Martial Adept (p. 168). The superiority die is added to any others you have, no matter when you gain them.
Some people took this to mean that the superiority die from Martial Adept still scaled with a Battle Master's regular superiority dice, with the only perceived change being that the superiority die scaled with Battle Master levels whether they were taken before or after taking the feat.
However, the wording of the feat in all printings since that 2015 errata is actually identical to the current (2018) version of the Martial Adept feat (this Reddit thread shows the same wording as below); the 2018 errata simply includes an exact quote of the change now.
The relevant portion of the Martial Adept feat now says (emphasis mine):
You gain one superiority die, which is a d6 (this die is added to any superiority dice you have from another source).
What this actually means is that Martial Adept's additional superiority die doesn't scale with Battle Master levels; the character with the feat simply has a separate d6 superiority die. (Battle Masters with the feat can expend either their regular superiority dice or their extra superiority die from the feat to use their maneuvers.)
It's arguable whether people were just misinterpreting how the errata previously paraphrased the change or whether the 2015-2017 errata misleadingly paraphrased it. (Mike Mearls' incorrect tweet supporting the misconception certainly didn't help.) Either way, it's now clear because the errata PDF quotes the exact wording of the change instead.