The School of Abjuration wizard's Projected Ward feature (PHB, p. 115) says:
Starting at 6th level, when a creature that you can see within 30 feet of you takes damage, you can use your reaction to cause your Arcane Ward to absorb that damage. If this damage reduces the ward to 0 hit points, the warded creature takes any remaining damage.
Does this mean that you can only absorb damage from one attack using this feature?
As you have noted, the projected ward feature states (emphasis mine):
...when a creature that you can see within 30 feet of you takes damage, you can use your reaction to cause your Arcane Ward to absorb that damage.
The rules for reactions state:
When you take a reaction, you can't take another one until the start of your next turn.
So, if a creature takes damage from an attack, and you use the projected ward feature, then you won't have a reaction available to use until the start of your next turn. Thus, if another creature takes damage, you could not absorb that damage using this feature.
However, once you regain your reaction, nothing stops you from using the ward again as long as it has hit points remaining and you meet the range and sight requirements for the feature.
1 I use the term "attack" a bit loosely here. The projected ward can be used any time a creature takes damage, including against effects that aren't attacks; like saving throws against the fireball spell. When I say "attack" here, I'm including any process that deals damage, not just those that are delivered through attack rolls.
You are correct. Projected Ward uses your reaction, and you only get one reaction per round. Hence, you can only absorb one attack (or one other source of damage) per round using this ability. If you were imagining that you could extend the normal benefits of your ward (i.e. continuous damage absorption) to another person for some amount of time, that's not how this ability works.
