sun protection factor

1 3.5

A number that shows how well sunscreen protects your skin from the sun's harmful rays

noun
/sʌn prəˈtɛkʃən ˈfæktər/

Specialized

: factor de protección solar

Dr. Epps advises using a sunscreen with an sun protection factor (SPF) of 15 or higher.
sun protection factor (SPF)
sunscreen with a sun protection factor
sun protection factor of 15

So what is SPFSPF is sun protection factor and really what it means is how long can you stay out in the sun without getting a sunburn.

Examples

I've never used foundation, but from Chanel, I use the eye cream and day cream with sun protection factor.

Blog text (33)
So what is SPFSPF is sun protection factor and really what it means is how long can you stay out in the sun without getting a sunburn.

Harper's BAZAAR
Doses within these intervals are constant, and childhood dose is influenced by the sun affinity ratio and the sun protection factor.

Academic text (1998)
The sun protection factor (SPF) is the use or nonuse of an SPF-15 sunscreen, which was deemed to have an effective SPF of 7.5 or 2, depending on use and application factors.

Academic text (1998)
Most experts agree that a minimum sun protection factor of 15 is required for effective protection.
Choose a sunscreen with a sun protection factor (SPF) of 30 or 45, and apply it evenly.

Synonyms

SPF

vssun protection factor

18 4.3

A number that shows how well sunscreen protects your skin from the sun

is the full written name rather than the abbreviation

Surface Forms

sun protection factor singular

sun protection factors plural

Morphology

sun + protection + factor

The meaning is directly and compositionally built from 'sun' (the star), 'protection' (preventing harm) and 'factor' (a measure or element) — i.e. a measure of protection against the sun. This is a straightforward noun phrase pattern found across many languages (e.g. French 'facteur de protection solaire'), so a B1 learner who knows the constituent words will readily infer the MWE's meaning.

Etymology

The term sun protection factor comes from a simple idea: the sun can make skin 'burn', protection is what a cream gives, and factor is a number that shows how much longer you can stay in the sun without 'burning' compared to no cream. So the number tells you how strong the sunscreen's 'protection' is.