Ayurveda sorts foods, seasons, activities and people into the same set of categories. Understanding what those categories are built from explains why the system resists translation into nutritional terms.
Classification is by observed quality
The base units are qualities perceptible without instruments: hot and cold, heavy and light, dry and moist, rough and smooth.
A food is described by the qualities it appears to carry, which include how it is grown, how it is prepared and how it feels to eat.
This is a coherent scheme built on what a practitioner could observe directly, and it predates any means of measuring composition.
Three functional groupings organise everything else
Qualities are gathered into three functional groupings, each associated with a type of activity: movement, transformation and structure.
These groupings are applied at every scale. A season, a time of day, a stage of life and a meal can each be described in the same terms.
The consistency is the point. A single vocabulary lets a practitioner relate a person's circumstances to their surroundings without switching frameworks.
Constitution describes a baseline, not a condition
A person is described as having a characteristic balance of the three groupings, treated as a stable individual baseline.
Departures from that baseline, rather than departures from a population average, are what the system attends to.
This is structurally different from a diagnostic model based on reference ranges, and it is one reason the two frameworks talk past each other.
Diet, routine and season are one subject
Ayurvedic texts treat daily routine, seasonal adjustment and food as a single continuous topic rather than separate disciplines.
Recommendations are consequently conditional: an ingredient suits one person in one season and is discouraged for another.
General statements of the form that a food is good or bad have no place in the scheme, because the classification only operates relative to a context.
Why the vocabulary resists translation
Terms are usually rendered into English as approximate equivalents, and each rendering drops part of the original meaning.
Words that describe a quality, a process and a bodily function simultaneously have no single-word counterpart, so translations tend to fix on one sense.
Practitioners generally keep the original terms for this reason, treating them as technical vocabulary rather than as words awaiting a better translation.