can include vocalising; turning/pushing/moving away; leaning/moving/reaching towards; frowning; smiling; blinking; looking at/touching/person; guiding person's hand; pointing to/touching desired object
Informal units are not part of a standardised system of units for measurement. For example, an informal unit for length could be paperclips of uniform length. An informal unit for area could be uniform paper squares of any size. Informal units are sometimes referred to as non-standard units.