Probably the first two “sciency” words anyone learns when entering the world of breeding is phenotype and genotype. An animal’s phenotype is what we can see or measure—eg coat colour, wool length, milk production. Its genotype is its genes that create that phenotype. Dominant, co-dominant and recessive genes all factor in genotypes, and we’ll cover these in more depth later.

Another word common in breeding is trait. People often use the words trait and phenotype interchangeably, but they are really two distinct things.
A trait is something that can be measured or observed.
A phenotype is the value for that trait.

Examples:

• Staple length in wool animals is a trait, “110mm/year” is a phenotype
• Temperament is a trait, “placid” is a phenotype
• Milk production is a trait, “6,000 litres/year” is a phenotype

Another thing worth clarifying is that people also tend to use the word “phenotype” to mean appearance. Coat colour is a classic example of this type of phenotype, and probably the one “everyone” learns in high school biology. But phenotype can also refer to performance. Speed (eg of Thoroughbreds and greyhounds) is an example of this type of phenotype. So is milk yield. The words phenotype and performance are interchangeable when referring to measurable traits as opposed to observable ones.

To summarise:
If it can be observed, it’s a trait.
If it can be measured, it’s a trait as well.
The value of a trait is a phenotype, and a phenotpye can refer to appearance or performance.

One last point to make: an animal has as many phenotypes as it has measurable and observable traits.