Kairos is an ancient Greek word meaning 'the right or critical moment'. In modern Greek, kairos also means 'weather' or 'time'.
Kairos relief, copy of Lysippos, in Trogir (Croatia)
Kairos as portrayed in a 16th-century fresco by Francesco Salviati
Modern Cairo relief by Dutch artist Janny Brugman-de Vries on the former Alexander Hegius gymnasium on the Nieuwe Markt in Deventer in the Netherlands
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions.
The flow of sand in an hourglass can be used to measure the passage of time. It also concretely represents the present as being between the past and the future.
Horizontal sundial in Canberra
24-hour clock face in Florence
A contemporary quartz watch, 2007