Sensu

Sensu is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular concept, but it also appears in expressions that indicate the convention or context of the usage.

Sensu is the ablative case of the noun sensus, here meaning "sense". It is often accompanied by an adjective (in the same case). Three such phrases are:

Søren Kierkegaard uses the phrase sensu eminenti to mean "in the pre-eminent [or most important or significant] sense".

When appropriate, comparative and superlative adjectives may also be used to convey the meaning of "more" or "most". Thus sensu stricto becomes sensu strictiore ("in the stricter sense" or "more strictly speaking") and sensu strictissimo ("in the strictest possible sense" or "most strictly speaking").

Current definitions of the plant kingdom (Plantae) offer a biological example of when such phrases might be used. One definition of Plantae is that it consists of all green plants (comprising green algae and land plants), all red algae and all glaucophyte algae; the group defined in this way could be called Plantae in sensu lato (or simply Plantae sensu lato). A stricter definition excludes the red and glaucophyte algae; the group defined in this way could be called Plantae in sensu stricto. An even stricter definition excludes green algae, leaving only land plants; the group defined in this way could be called Plantae in sensu strictiore, or Plantae in sensu strictissimo.

Conversely, where convenient, some authors derive expressions such as "sensu non strictissimo", meaning "not in the narrowest possible sense".

A similar form is in use to indicate the sense of a particular context, such as "Nonmonophyletic groups are ... nonnatural (sensu cladistics) in that ..." or "... computation of a cladogram (sensu phenetics) ..."

Also the expression sensu auctorum (abbreviation: sensu auct.) is used to mean "in the sense of certain authors", who can be designated or described. It normally refers to a sense which is considered invalid and may be used in place of the author designation of a taxon in such a case (for instance, "Tricholoma amethystinum sensu auct." is an erroneous name for a mushroom which should really be "Lepista personata (Fr.) Cooke").