Player Core Chapter 8: Playing The Game Encounter Mode

Turns

When it's your turn to act, you can use single actions ([one-action]), short activities ([two-actions] and [three-actions]), reactions ([reaction]), and free actions ([free-action]). When you're finished, your turn ends and the character next in the initiative order begins their turn. Sometimes it's important to note when during your turn something happens, so a turn is divided into three steps.

The GM keeps track of the initiative order for an encounter. It's usually okay for the players to know this order since they'll see who goes when and be aware of one another's results. However, the GM might want to conceal information about adversaries the PCs have yet to detect or identify.
Once the encounter's order is set, it's usually not necessary to track the original initiative numbers. The GM can create a simple list, use a series of cards or other indicators, or use a Starfinder Combat Pad, which has magnetic markers to allow for easily rearranging the order.

Changing The Initiative Order

Any method used to track the initiative order needs to be flexible because the order can change. A creature can use the Delay basic action to change its place in the order, in which case you can erase it from the list or pull its marker aside until it reenters the initiative order. When a creature gets knocked out, its initiative order also changes. Using the Ready basic action doesn't change a creature's place in the initiative order, though, because the designated action becomes a reaction.

Step 1: Start Your Turn

Source Player Core pg. 427

Many things happen automatically at the start of your turn— it's a common point for tracking the passage of time for effects that last multiple rounds. At the start of each of your turns, take these steps in any order you choose.

If you created an effect lasting for a certain number of rounds, reduce the number of rounds remaining by 1. The effect ends if the duration is reduced to 0. For example, if you cast a spell that lasts 3 rounds on yourself during your first turn of a fight, it would affect you during that turn, decrease to 2 rounds of duration at the start of your second turn, decrease to 1 round of duration at the start of your third turn, and expire at the start of your fourth turn.
You can use 1 free action or reaction with a trigger of “Your turn begins” or something similar.
If you're dying, roll a recovery check.
Do anything else that's specified to happen at the start of your turn, such as regaining Hit Points from fast healing or regeneration.

The last step of starting your turn is always the same.

Regain your 3 actions and 1 reaction. If you haven't spent your reaction from your last turn, you lose it—you can't “save” actions or reactions from one turn to use during the next turn. Some abilities or conditions (such as quickened, slowed, and stunned) can change how many actions you regain and whether you regain your reaction. (Details on gaining and losing actions are here.)

Step 2: Act

Source Player Core pg. 428

You can use actions in any order you wish during your turn, but you have to complete one action or activity before beginning another; for example, you can't use a single action in the middle of performing a 2-action activity. What actions you can use often depend on your class features, skills, feats, and items, but there are default actions anyone can use, described in Basic Actions. Some effects might prevent you from acting. If you can't act, you can't use any actions, including reactions and free actions.
If you begin a 2-action or 3-action activity on your turn, you must be able to complete it on your turn. You can't, for example, begin to High Jump using your final action on one turn and then complete it as your first action on your next turn.
Once you've spent all three of your actions, your turn ends (as described in Step 3) and the next creature's turn begins. You can choose to end your turn early, losing all remaining actions (but not your reaction).

Step 3: End Your Turn

Source Player Core pg. 428

Once you've done all the things you want to do with the actions you have available, you reach the end of your turn. Take the following steps in any order you choose. Play then proceeds to the next creature in the initiative order.

End any effects that last until the end of your turn. For example, spells with a sustained duration end at the end of your turn unless you used the Sustain a Spell action during your turn to extend them. Some effects caused by enemies might also last through a certain number of your turns, and you decrease the remaining duration by 1 during this step, ending the effect if its duration is reduced to 0.
If you have a persistent damage condition, you take the damage at this point. After you take the damage, you can attempt the flat check (in the sidebar) to end the persistent damage. You then attempt any saving throws for ongoing afflictions. Many other conditions change at the end of your turn, such as the frightened condition decreasing in severity. These take place after you've taken any persistent damage, attempted flat checks to end the persistent damage, and attempted saves against any afflictions.
You can use 1 free action or reaction with a trigger of “Your turn ends” or something similar.
Resolve anything else specified to happen at the end of your turn.