retard

Everyday

1. (formal, science) To slow down or delay something: to retard growth, fire-retardant material. tree →
2. (rude, offensive) A very hurtful insult for a person with a learning disability or for someone thought stupid — never use it. tree →

In the lessons

In science and safety «retard» means slow down; «fire retardant» fabric slows burning, which keeps people safe. The insult sense is hate speech: in stories it shows a bully being cruel; in real life using it hurts people with disabilities. Old medical words like «mentally retarded» are now replaced by «learning disability» or «intellectual disability».

Examples

• Cold weather retards the growth of plants. tree →
• The curtains are treated to retard fire. tree →
• Fire-retardant pyjamas are safer for children. tree →
• Salt can retard the rotting of meat. tree →
• (rude, a bully in a story) «Don't call him that word — it's cruel,» said the teacher. tree →

Note

The slur is one of the most hurtful words in English; do not use it, even as a joke. Safe words: slow, delay; «retardant» (a substance that slows burning). In music, «ritardando» means getting slower.