無 (wú) means ‘negative, not, without’; 形 (xíng) means ‘appearance, form, shape.’ 無形 means not just invisible, but intangible. To illustrate: the poet Zhang Shunmin of the Northern Song dynasty wrote once that ‘詩是無形的畫, 畫是有形詩’; that poems were incorporeal (wúxíng) paintings, and paintings were corporeal poems.
