Concise answer
Hair fall describes shedding; hair thinning describes reduced visible density or calibre. A person can have one without noticing much of the other.
Pattern hair loss may progress through miniaturisation without dramatic shedding. Temporary shedding may be heavy but later recover if the trigger resolves.
History, scalp examination and comparable photographs help separate these patterns.
When evaluation may help
Seek assessment when shedding persists, the part widens, the hairline recedes or loss is patchy or symptomatic.