| def: The units of measure for the x-axis of a (1D or 2D) FID, (1D or 2D) pre-processed spectrum, 2D projected spectrum, and (1D or 2D) post-processed spectrum. altdef: The units used to represent either time domain (for a FID) or the frequency domain (for a spectrum). | 
| •owl:Thing | 
| •entity | 
| •continuant | 
| •dependent_continuant | 
| •realizable_entity | 
| •cardinal_part_of_design_specification | 
| •cardinal_part_of_protocol | 
| •protocol_parameter | 
| •x-axis_unit |