Most of us have accidentally knocked our ball off the tee when setting up for our drive. Invariably, we have had somebody comment, “That’s one.” Is it a stroke? Does it count? No.
Rule 6.1a tells us that we start a hole by making a stroke and a stroke, by definition, is the forward movement of the club with the intent to hit the ball. Knocking the ball off the tee by accident is not intent to hit the ball so it doesn’t count as a stroke. Put the ball back on the tee and hit away with no penalty.
The teeing area is a special part of the golf course. The teeing area is a rectangle with the corners being the front edges of the tee markers and two club lengths backwards. You can alter the surface, move bend or break grass, remove dew or press down grass or dirt within the teeing area before you start the hole. If you make a stroke (with intent and it counts!) at the ball on a tee and barely make contact or even whiff it and the ball stays within the teeing area you have many more options than you did before the 2019 rules changes. You can pick it up and move it anywhere within that teeing area with no penalty to make your next stroke. You can even tee it up again or substitute a new ball! The new rules made the teeing area kind of a free for all in many respects and knowing this rule can be used to your advantage.