  We review the terms, spectral radiance and spectral irradiance, and show how
their precise definitions are crucial for interpreting observations made with
different instruments covering widely different energy or wavelength ranges. We
show how the use of column and volume emission measures in different solar
physics and astrophysics communities has led to confusion in relating measured
extreme ultraviolet and soft X-ray spectra with theoretical spectra generated,
in particular, using CHIANTI. We describe a method for obtaining spatially
integrated X-ray line and continuum spectra using CHIANTI that requires a
column emission measure when only the plasma temperature and volume emission
measure, but not the source area, are known from observations.
