Arupa

Arūpa (Sanskrit) refers to formless (perhaps non-physical) or also non-material objects or subjects.

For example, space (ākāśa) is somewhat arūpa, while the four primary elements are rupa. (check this)

See also:

• Arūpadhātu - formless realm
• Arūpajhāna
• Ārūpyāvacaradhyāna