Apply suggestions from code review

Co-authored-by: Richard Höchenberger <richard.hoechenberger@gmail.com>

src/02-common-principles.md

@@ -48,15 +48,15 @@ misunderstanding we clarify them here.
     subject performed multiple conceptually different behaviors (with different
     sets of instructions) they will be considered one (combined) task.
 
-1.  **Event** - something that happens or may be perceived as happening at a particular
-    moment during the recording.
-    Events are most commonly associated with sudden-onset sensory stimulus presentations
-    or with the distinct onset of a subject motor action.
+1.  **Event** - something that happens or may be perceived by a test subject as happening at a particular
+    instant during the recording.
+    Events are most commonly associated with on- or offset of stimulus presentations,
+    or with the distinct on- or offset of a subject's response or motor action.
     Other events may include unplanned incidents,
     changes in task instructions or experiment control parameters,
     and noted data feature occurrences.
     In BIDS, each event has an onset time and duration.
-    Note that not all tasks will have recorded events (e.g., "resting state").
+    Note that not all tasks will have recorded events (e.g., recordings of "resting state" activity).
 
 1.  **Run** - an uninterrupted repetition of data acquisition that has the same
     acquisition parameters and task (however events can change from run to run