Question

what is a river pattern (answer in about 100 to 150 words )

Answer 1

River patterns are those patters formed by rivers in a particular drainage  basin

OR

The form, in which a stream is seen, is known as river pattern.

The 4 patterns formed by rivers drainage basin:

RADIAL PATTERN - Commonly found where the rivers flow outwards in all directions and downhills from a high point .

CENTRIPETAL PATTERN - The opposite of radial pattern . The stream drain into a basin or depression or a crater lake. The pattern resembles the spoke of a bicycle wheels.
TRELLIS PATTERN - The tributaries flow along the areas of less resistant rock and join the main river at right angles.Commonly found in area of alternating bands of resistant and less resistant rocks.
DENDRITIC PATTERN - When tributaries join the main river at an acute angle.Resembles branches or vein of a leaf.

Answer 2

River patterns are those patters formed by rivers in a particular drainage basin
OR
The form, in which a stream is seen, is known as river pattern.

The 4 patterns formed by rivers drainage basin:
RADIAL PATTERN - Commonly found where the rivers flow outwards in all directions and downhills from a high point .
CENTRIPETAL PATTERN - The opposite of radial pattern . The stream drain into a basin or depression or a crater lake. The pattern resembles the spoke of a bicycle wheels.
TRELLIS PATTERN - The tributaries flow along the areas of less resistant rock and join the main river at right angles.Commonly found in area of alternating bands of resistant and less resistant rocks.
DENDRITIC PATTERN - When tributaries join the main river at an acute angle.Resembles branches or vein of a leaf.