Petrol, power tools, cups of tea and tradesmen can cause odd damage and dead patches in the lawn.
All grasses, including lawn grasses, produce seed heads, with some being more numerous and noticeable than others - one of those is rye grass.
Lawn burn or scorch from fertiliser, weed killer or dog pee causes degrees of damage from yellowing of the grass to killing areas of lawn.
How to stop dead patches being caused by dog or bitch urine and how to repair them if you're not paying attention.