The Spanish word 'día' meaning 'day' comes directly from the Latin word 'dies', which also meant 'day'. This is a straightforward etymology where the Latin word evolved into Spanish with minimal changes in both form and meaning. The main change was the loss of the final '-s' and the addition of the accent mark on the 'i' to maintain the stress pattern in Spanish.

Some common Spanish words derived from the same Latin root include: 'diario' (daily), 'mediodía' (noon/midday), and 'cotidiano' (daily). These words all maintain a connection to the concept of 'day' while taking on more specific meanings.

While English 'day' comes from Germanic roots rather than Latin, there are several English words related to the Latin 'dies', including: 'diary' (a daily record), 'diurnal' (relating to or occurring in the day), and 'meridian' (from Latin 'meridies' meaning 'midday'). The word 'diet' in the sense of a daily assembly also comes from this root, though its meaning meaning 'food regime' has a different etymology.