Cascade means to fall over a steep surface or over an edge. Water is especially prone to cascading off of cliffs and forming waterfalls.
A case is something that goes around something else, for storage and protection. Expensive things that need to be kept safe are usually kept in cases. The picture is of a violin and its case, but it is common to see guitar cases and glasses cases too.
Case might also be a word for a situation or the state of things, as in "take some money in case you need it".
Scientific name: anacardium occidentale
The cashew, or caju, is a small tree native to Brazil. Cashew nuts are the seeds of the cashew apple, and are found in the grey bump at the end of the fruit in the picture. The cashew apple itself is sweet, soft and juicy.
Cashews are usually sold roasted and salted and eaten as a snack.
A cask is a reasonably small container, usually used for storing alcoholic drinks. Casks are usually shaped like a small barrel, although the term is often applied to cheaper boxed wine too.
Scientific name: casuarius casuarius
Cassowaries are very large flightless birds that live in tropical forests of New Guinea and northeastern Australia. The only birds bigger than the cassowary are the ostrich and emu.
Cassowaries mainly eat fruit, but will also eat new shoots, seeds and fungi, insects and small animals. Cassowaries usually travel around on their own except when it is time to find a mate and lay eggs.
The booming noise the cassowary makes is the lowest known bird call, and is so low humans can only just hear it.