What do the fabric care symbols on clothing labels mean?

They are a standardised international system, and once you know the five base shapes the rest follows logically.

The five symbols:

A tub of water — washing. A number inside gives the maximum temperature in Celsius; dots give the same information (one dot 30°, two 40°, three 50°, and so on). A hand in the tub means hand wash only. A bar underneath means a reduced or synthetics cycle; two bars means a gentle or delicate cycle. A crossed-out tub means do not wash.

A triangle — bleaching. Plain triangle means any bleach is permitted. Two diagonal lines inside means only oxygen or non-chlorine bleach. Crossed out means no bleach.

A square — drying. A circle inside the square means tumble drying: one dot is low heat, two is normal, crossed out means do not tumble dry. Lines inside a plain square indicate natural drying — a vertical line means line dry, a horizontal line means dry flat (important for knitwear, which stretches if hung), and a diagonal line in the corner means dry in the shade.

An iron — ironing. Dots give maximum temperature: one is cool for synthetics, two is medium for wool and blends, three is hot for cotton and linen. Crossed-out steam lines beneath mean do not use steam. Crossed out entirely means do not iron.

A circle — professional cleaning. A letter inside tells the dry cleaner which solvent to use — P and F for different solvent types, W for professional wet cleaning. A bar underneath indicates a gentler process. Crossed out means do not dry clean.

The general logic: a cross through any symbol means do not do it, and bars beneath always mean be gentler.

A useful rule: the label states the maximum, not a requirement — washing cooler is always permitted.