Words that start with S

A slingshot is a weapon made from a Y-shaped arm with an elastic band connecting the two arms. There is usually a pocket for a stone or other projectile in the centre of the band. Slingshots can be very accurate, and can be used to hunt small game.

Something is slippery if it very hard to get a hold of, or you can't stick to it. A slippery surface is one your shoes or feet don't grip onto, so you fall over when you are walking on them. Slippery things are usually very smooth and are often wet and slimey.
Some things that are slippery are ice, wet roads, banana peels, and rocks at the beach at low tide that have algae growing on them.
The opposite of slippery is sticky.

Something is sloped if it has an angle some way off horizontal. The car in the picture has been parked on a road with a slope.

Sloths are a large animal that spends almost all of its time up trees, hanging from branches by its large curved claws. Sloths sleep for around 18 hours a day. They move very slowly - around 1-5 feet per minute.
They are related to armadillos and anteaters.

Sloth is the sin of laziness and indifference; not even caring about doing anything.

You slouch when you stand with a slightly drooping posture, with your shoulders forward and your stomach sticking out.

The slow loris are a group of nocturnal primates. They move slowly, and live in forests in parts of Southeast Asia. They are the only primate with a toxic bite.

A slum is a place where very poor people live. Slums are usually filled with rubbish and have a very large number of people living in them.

You smack someone when you hit them with your open hand. The cat in the picture is smacking the other cat.
A smack is also a small amount of something, for example "this jelly smacks of garlic".
A similar word to smack is slap, trace, hint or suggestion.

Smart is another word for intelligent. A smart person learns quickly and can do or build complex things.