What is the meaning of ο?

The lower case letter called omicron (όμικρον); The 15th letter of the Greek alphabet.

The cardinal number 70 in Greek numerals.

The cardinal number 70,000 in Greek numerals.

Lower-case omicron (ὂ μικρόν), the 15th letter of the ancient Greek alphabet. It represented the close-mid back rounded vowel /o/. It is preceded by ξ and followed by π.

the

the

the definite masculine singular article. the

Source: wiktionary.org