Questions about second wind

I'm a new GM running Curse of Strahd - one of my players is a fighter and insists he can use second wind repeatedly in the same fight, up to 3 times, since it says 3 times per long rest in the description  

To me, this reads it can be used twice before a short rest. Another player in the group insisted it can only be used once per short rest. I'd love some clarity if anyone can chime in.

Thanks in advance for any assistance. 

In 5E once you used Second Wind, you must finish a short or long rest before you can use it again.

In 5.5E you can use Second Wind  twice (3 at level 4+ and 4 times at level 10+) and regain one expended use when you finish a Short Rest, and you regain all expended uses when you finish a Long Rest.

So depending which version of the Fighter & level is in play, the number of uses will vary.

• 2014 Fighter level 01-20 = 1 Second Wind before resting.
• 2024 Fighter level 01-03 = 2 Second Wind before resting.
• 2024 Fighter level 04-09 = 3 Second Wind before resting.
• 2024 Fighter level 10-20 = 4 Second Wind before resting.

Thank you for the reply, just for my own clarity: at lvl 5 my fighters can use second wind 3 times total per LR. If they want to use all 3 in one combat, no restrictions? 

I appreciate the help, trying to learn DND rules and GM at the same time has been challenging. 

Quote from billysjr >>

Thank you for the reply, just for my own clarity: at lvl 5 my fighters can use second wind 3 times total per LR. If they want to use all 3 in one combat, no restrictions? 

I appreciate the help, trying to learn DND rules and GM at the same time has been challenging. 

 Your level 5 Fighter can use 3 Second Wind per Long Rest and one more whenever they complete  Short Rest before that.

Quote from billysjr >>

Thank you for the reply, just for my own clarity: at lvl 5 my fighters can use second wind 3 times total per LR. If they want to use all 3 in one combat, no restrictions? 

I appreciate the help, trying to learn DND rules and GM at the same time has been challenging. 

With the 5.5e rules, it's better not to think of it as "3 times total per LR", because that's not really correct; it could end up being more than that depending on how many short rests you take during the day. 

Think of it like this. A level 5 Fighter has a maximum of three Second Wind "charges". Taking a Short Rest recharges one spent charge. Taking a Long Rest recharges all of the spent charges. There's no limit on how many charges you can spend in a single combat, other than how many you have to begin with.

I don't know if the next detail is useful for you, billysjr, but just in case.

Apart from the information already provided by Plaguescarred and wagnarokkr, Second Wind is also interesting when used for the Level 2: Tactical Mind and Level 5: Tactical Shift features, as explained in the article 2024 Fighter vs. 2014 Fighter: What’s New:

Second Wind — Level 1

Second Wind starts at two uses and increases as you level up. Each Short Rest, you regain one expended use of the feature. On a Long Rest, you regain all expended uses. Thanks to Tactical Mind and Tactical Shift, this resource has also been made effective even when you’re not on the edge of death!

Tactical Mind — Level 2

When you fail an ability check, you can expend a use of Second Wind to gain 1d10 to add to the roll. Plus, your Second Wind usage isn’t expended if you still fail. Who said jocks can’t be smart?

Tactical Shift— Level 5

If your caster buddy is getting pummeled across the battlefield but you can’t risk an Opportunity Attack to get to them, all you need to do is use Second Wind as a Bonus Action. With Tactical Shift, using your Second Wind allows you to move up to half your Speed as part of the Bonus Action, and you don’t provoke Opportunity Attacks.