When the nature of contact between the element of a pair is such that it can turn or revolve about a fixed axis, the pair is known as a turning pair.

When the nature of contact between the element of a pair is such that it can only slide relative to the other, the pair is known as a sliding pair and can be found in piston and cylinder of a reciprocating steam engine.

The ball and socket joint is an example of spherical pair. When the two elements of a pair are connected in such a way that one element turns or swivels about the other fixed element, the pair formed is called a spherical pair.

When the nature of contact between the element of a pair is such that it can only slide relative to the other, the pair is known as a sliding pair and it has a completely constrained motion.

When the nature of contact between the element of a pair is such that one element can turn abut the other by screw threads, the pair is known as a screw pair. The lead screw of a lathe with nut is an example of screw pair.

When the two elements of a pair have surface contact when relative motion, takes place and the surface of one element slides over the surface of the other, the pair formed is known as lower pair. It will be seen that sliding pairs, turning pairs and screw pairs form lower pairs.

When the nature of contact between the element of a pair is such that one element can turn abut the other by screw threads, the pair is known as a screw pair. When the nature of contact between the element of a pair is such that it can only slide relative to the other, the pair is known as a sliding pair.

When the two elements of a pair are constrained in such a way that one can only turn or revolve about a fixed axis of another link, the pair is known as turning pair.

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When the nature of contact between the element of a pair is such that one element can turn abut the other by screw threads, the pair is known as a screw pair.