Semantic molecules
Semantic primes can be thought of as simple and irreducible "atoms" of meaning. But although the whole enterprise of NSM semantics rests ultimately on semantic primes, NSM researchers recognise that some explications necessarily incorporate certain complex semantic units, termed "semantic molecules". These are non-primitive meanings (hence, ultimately decomposable into semantic primes) that function as units in the semantic structure of other, yet more complex words. The notion is similar to that of "intermediate-level concepts" in the Moscow School of Semantics, with the constraint that semantic molecules must be meanings of lexical units in the language concerned.
From a conceptual point of view, the NSM claim is that some complex concepts are semantically dependent on other less complex, but still non-primitive, concepts. For example, semantic explications for words like 'sparrow' and 'eagle' include 'bird' as a semantic molecule. The cognitive claim is that the concept of 'sparrow' includes and depends on the concept of 'bird'. In this case, the relationship is taxonomic: 'sparrows' and 'eagles' are both 'birds [m] of one kind' (molecules are marked in explications with the notation [m]). Many semantic molecules are taxonomic superordinates, but semantic molecules can enter into semantic structures in many other ways. For example, explications for 'walk' and 'run' include 'feet [m]' and 'ground [m]', where the relationships are, roughly, body-part instrumental and location, respectively. Explications for 'cut' and 'chop' include 'sharp [m]', where the molecule characterises the nature of a physical instrument. Explications for 'fork', 'spoon' and 'plate' include 'eat [m]', where the relationship relates to intended purpose or function.
It has to be stressed that whether or not a given word-meaning is a semantic molecule is an empirical issue, it is not arbitrary or a matter of convenience. The sole criterion is semantic necessity, and this can only be determined by detailed semantic analysis.
Many semantic molecules are language-specific, but it appears that a limited number, perhaps 60-80, may be universal or near-universal. These include some body-part words, such as 'mouth' and 'hands', some environmental terms, such as 'sky', 'ground', 'fire' and 'water' and some basic social categories, such as 'children', 'women', and 'men'. Semantic molecules be "nested", enabling a great compression of semantic complexity. Research into semantic molecules is still at a relatively early stage, with many interesting research questions as yet unanswered. Some proposed universal semantic molecules are shown in the table below:
Selection of proposed universal semantic molecules
| hands, mouth, eyes, head, ears, nose, face, teeth, fingers, breast, skin, bones, blood | Body parts |
| long, round, flat, thin, hard, soft, sharp, smooth, heavy | Physical |
| be on something, at the top, at the bottom, in the middle, in front of, around | Spatial / physical |
| sky, the Earth, sun, moon, stars, ground, during the day, at night, | Environmental |
| day | Times |
| water, fire | Fire and water |
| creature, grow, egg, tail, wings, feathers | Biological |
| children, men, women, be born, mother, father, wife, husband | Biosocial |
| wood, stone | Materials |
| know (someone), be called | "Knowing" and "naming" |
| hold, make, kill, breathe, sleep, sit, lie, stand, play, laugh, sing | "Doing" |
It is worth adding that sometimes NSM explications make use of complex terms of a different kind; namely, derivational bases. For example, the explication for a derived word like 'illness' includes the base element 'ill [d]', where the notation [d] marks its status as a derivational base. The secondary or extended senses of a lexeme sometimes incorporate its primary sense, and, when this occurs, the base meaning is also marked with [d]. To clarify the difference between semantic molecules and derivational bases, one can say that derivational bases have a highly localised and specialised provenance, i.e. each one is confined to a handful of semantically related words. Semantic molecules, on the other hand, range widely across the lexicon. It can also be noted that the concept of semantic molecules is an NSM innovation, whereas the idea that derived forms are semantically built on the meanings of their base forms is commonly accepted in linguistics.