Bit: This is an abbreviated term for “binary digit”. This is the smallest unit of information in the binary numbering system. It represents a choice between two possible and equally likely values. It is often used to represent an on/off or true/false state.
Word: This is a group of smaller units in the binary numbering system. This group is treated as one unit. Most programmable logic controllers use either 8, 16 or 32 smaller units to form this.