By way of a first definition, a '''higher order sign relation''' is a sign relation, some of whose signs are '''higher order signs'''. If an extra degree of precision is needed, higher order signs can be distinguished in a variety of different ''species'' or ''types'', to be taken up next. | By way of a first definition, a '''higher order sign relation''' is a sign relation, some of whose signs are '''higher order signs'''. If an extra degree of precision is needed, higher order signs can be distinguished in a variety of different ''species'' or ''types'', to be taken up next. |