Final answer:
Trichorrhexis nodosa is the condition characterized by brittleness and the formation of nodular swellings along the hair shaft, not to be confused with alopecia, dandruff, or psoriasis.
Step-by-step explanation:
The condition characterized by brittleness and the formation of nodular swellings along the hair shaft is known as Trichorrhexis nodosa. This is not to be confused with alopecia, which is hair loss, or dandruff, a condition that causes the scalp to flake, or psoriasis, which is a skin condition that causes red, itchy scaly patches. Trichorrhexis nodosa can occur due to a variety of factors, such as physical or chemical damage to the hair. Hair that is undernourished during the anagen phase, or active phase of the hair growth cycle, can be particularly susceptible to this condition.