Here's why:
* Old English: In Old English, the second-person pronoun was "þū" for singular and "gē" for plural.
* Middle English: During the Middle English period (roughly 1150-1500), the singular "þū" started to decline in usage, especially in formal contexts. It was replaced by the plural form "gē" (pronounced similarly to "ye").
* Modern English: By the time of Modern English, the use of "gē" had solidified for both singular and plural. This is why we use "you" for both singular and plural today.
This shift in pronoun usage happened for a few reasons:
* Increased formality: In the Middle Ages, the use of "þū" became considered less respectful and more informal.
* Social change: A more egalitarian society may have contributed to the use of a singular pronoun, as using the plural form "gē" could be interpreted as a form of respect or deference.
While "you" is the most dramatic example, other pronouns have also undergone changes in pronunciation and usage since Old English. However, "you" is the only one that switched from a singular/plural distinction to a single form for both.