Find the odd number / letters / word from the given alternative.

Ink
Paper
Pen
Pencil E. Sharpener

The odd one out is E, sharpener. The other four items are all writing instruments, while a sharpener is a tool used to sharpen writing instruments.

Ink is a liquid or paste that is applied to paper or other surfaces with a writing instrument to produce writing or printing.

Paper is a thin, flexible material produced from cellulose fibers derived from wood pulp, rags, or grasses.

A pen is a handheld writing instrument that applies ink to a surface, usually paper, for writing or drawing.

A pencil is a writing implement that has a thin core of graphite enclosed in a wooden or metal casing.