Six synonyms, which are related words for the word "six" are multiplier and Sextuple, VI in Roman Numerals, Quantity and Half a dozen and group of six and Sextet or hexad.
Other related terms are Senary (base six system or hexagonal (six sided).
A list of 20 synonyms in English are:
Unique and Distinct.
Rich and Wealthy.
Meticulous and Thorough.
Lucrative and Profitable.
Keep and Retain.
Intelligent and Smart.
Happy and Joyful.
Genuine and Authentic.
Fast and Quick.
Enormous and Massive.
Difficult and Hard.
Delicious and tasty.
Capable and Able.
Calm and Peaceful.
Brief and Short.
Brave and Courageous.
Blend and Mix.
Achieve and Accomplish.
Accurate and Correct.
Abundant and Ample.
Synonyms are words that share the same meaning or even very similar meanings.