consider the Greek letters:
- alpha means beginning
- omega means end
- delta means change
- sigma means "in summary"

[Glossary of mathematical symbols - Wikipedia](https://en.wikipedia.org/wiki/Glossary_of_mathematical_symbols#Set_theory)

[Real number - Wikipedia](https://en.m.wikipedia.org/wiki/Real_number)
bold R

[Glossary of mathematical symbols - Wikipedia](https://en.wikipedia.org/wiki/Glossary_of_mathematical_symbols)

[Helen (unit) - Wikipedia](https://en.m.wikipedia.org/wiki/Helen_(unit))

[List of humorous units of measurement - Wikipedia](https://en.m.wikipedia.org/wiki/List_of_humorous_units_of_measurement)