How many types of crystal systems are there? Name them.

How many types of digestive system are there?

Name any two crystal system.

Name any two crystal systems.

In the adjoining figure, ABCD is a quadrilateral. (i) How many pairs of adjacent sides are there? Name them. (ii) How many pairs of opposite sides are there? Name them. (iii) How many pairs of adjacent angles are there? Name them. (iv) How many pairs of opposite angles are there? Name them. (v) How many diagonals are there? Name them.

(a) How many types of blood vessels are there in the human body ? Name them (b) Why does the heart need valves ?

The type of crystal system shown is

The type of crystal system shown is

How is the unit cell of crystal characterised? How many basic crystal systems are obtained on the basis of this characterisation?