Mr Moy, like many Tai ji teachers, told his students to relax. What he actually said was – 放 松.
松 is an essential quality for tai chi practitioners. It means loose, but the character also means a pine tree. You can see the pictographic representation of a tree in the left hand half of the character, with branches hanging down from the trunk – this is more clear in an older version of the character 枩 which has more branches. The branches hang loosely, but the tree retains its structure – something that is no longer implied by the word “relax” in English, which today could easily refer to someone collapsed on their sofa, with no structure.
放 means release. thus means something like “let go of all excess tension”.
Towards the end of his life, Mr Moy started telling his students, in English, to let go, a translation of which avoids the ambiguity of the word relax. I like to think of it as: relax and let go.