Sensu: Defining Precision in Scientific and Legal Terminology
In the worlds of science, law, and linguistics, precision is everything. A single term can have multiple interpretations depending on how strictly it is applied. To resolve this ambiguity, scholars use the Latin word sensu, which translates to "in the sense of." This qualifier allows experts to specify whether they are using a term in a narrow, broad, or context-specific manner.
Whether it is a biologist classifying a plant species or a geologist defining a stratigraphic stage, sensu provides a standardized way to communicate the boundaries of a concept, a process known as circumscription—the act of defining what is included in a group and what is excluded.
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Key Facts
- Sensu is the ablative case of the Latin noun sensus, meaning "sense."
- Sensu stricto (s.s.) refers to a strict or narrow definition.
- Sensu lato (s.l.) refers to a broad or inclusive definition.
- Sensu amplo is similar to sensu lato, meaning a relaxed or generous sense.
- Sensu auctorum refers to the sense used by certain authors, often indicating a definition now considered invalid.
- The term is essential for taxonomic circumscription to ensure clarity in biological and geological classifications.
Common Qualifiers and Variations
The term sensu is rarely used alone; it is typically paired with an adjective to qualify the scope of a definition. These qualifiers can be adjusted using comparative and superlative forms to indicate increasing levels of precision.
Strict, Broad, and Ample Senses
The most frequent pairings include sensu stricto (strict sense), sensu lato (broad sense), and sensu amplo (ample or relaxed sense). For instance, the philosopher Søren Kierkegaard utilized sensu eminenti to denote a "pre-eminent" or most significant sense.
Degrees of Precision
When a researcher needs to be even more specific, they may use comparative or superlative adjectives. For example, sensu stricto can become sensu strictiore ("in the stricter sense") or sensu strictissimo ("in the strictest possible sense").
| Base Phrase | Comparative | Superlative | General Meaning |
|---|---|---|---|
| sensu stricto | sensu strictiore | sensu strictissimo | Strict / Stricter / Strictest sense |
| sensu lato | sensu latiore | sensu latissimo | Broad / Broader / Broadest sense |
| sensu amplo | sensu ampliore | sensu amplissimo | Relaxed / More relaxed / Most relaxed sense |
Practical Applications in Science
Biological Taxonomy
In biology, sensu is critical for defining taxa (groups of organisms). Consider the plant kingdom, Plantae. A definition of Plantae sensu lato might include all green plants, red algae, and glaucophyte algae. However, Plantae sensu stricto would exclude red and glaucophyte algae. An even narrower definition, Plantae sensu strictissimo, might exclude green algae entirely, leaving only land plants.
Another example is the family Malvaceae. In a strict sense (s.s.), the family is cladistically monophyletic, meaning all members descend from a single most recent common ancestor (MRCA). In a broader sense (s.l.), the family might include other groups like Bombacaceae and Tiliaceae for historical convenience or practical utility.
Geology and Other Fields
While biology focuses on ancestry, geology uses sensu to handle regional interpretations. For example, the Kimmeridgian Stage has been interpreted as sensu anglico (the English meaning, based on English materials) or sensu gallico (the French/German meaning, based on continental materials).
In legal and linguistic contexts, these terms similarly help define whether a law or a word is being applied in its narrowest technical meaning or its broader common usage.
Author Citations and Context
Sometimes, a term is defined not by a level of strictness, but by a specific person. The phrase sensu [Author Name] (or sec., short for secundum, meaning "following") indicates that the meaning is based on that specific author's definition.
This is distinct from a nomenclatural author citation, which simply credits the person who first named a species. A sensu citation is used when a researcher wants to discuss a specific author's view of a group's circumscription, regardless of whether that view is currently accepted by the wider scientific community.
Frequently Asked Questions
What is the difference between sensu stricto and sensu lato?
Sensu stricto refers to a narrow, strict definition of a term, while sensu lato refers to a broad, inclusive definition.
What does sensu auctorum mean?
Sensu auctorum means "in the sense of certain authors." It is often used to refer to a definition or naming convention that is now considered invalid or erroneous.
How is sensu used in biological taxonomy?
It is used to specify the circumscription of a taxon, clarifying which species are included in a group based on different scientific interpretations or levels of inclusivity.
Can sensu be used outside of biology?
Yes. It is commonly used in geology to distinguish regional interpretations, as well as in law, linguistics, and semiotics to clarify the scope of a definition.
What is the meaning of "sec." in scientific citations?
Sec. is an abbreviation for the Latin secundum, meaning "following" or "in accordance with." It is used similarly to sensu to attribute a specific meaning to a particular author.