impact-- The period during which a ball is in contact with the clubface during a golf shot.

in-- The second nine holes on a golf course. The first 9 holes are referred to as "out".

in play-- A ball that is within the permitted confines of a golf course and that has been teed off but not holed out.

inside-- A golf ball that rests closer to the hole when compared to another ball.

interlocking grip-- A particular kind of golf grip in which the little finger of the left hand is intertwined with the index finger of the right hand for a right handed player and vice-versa for a left-handed player.

intended line-- The intened path of a golf ball.

iron-- A type of golf club with a head made from metal, or a composite material. Typically numbered from 1-9. Other club types are Woods (or metals), wedges and putters.