  Stratified turbulence shows scale- and direction-dependent anisotropy and the
coexistence of weak turbulence of internal gravity waves and strong turbulence
of eddies. Straightforward application of standard analyses developed in
isotropic turbulence sometimes masks important aspects of the anisotropic
turbulence. To capture detailed structures of the energy distribution in the
wave-number space, it is indispensable to examine the energy distribution with
non-integrated spectra by fixing the codimensional wave-number component or in
the two-dimensional domain spanned by both the horizontal and vertical wave
numbers. Indices which separate the range of the anisotropic weak-wave
turbulence in the wave-number space are proposed based on the decomposed
energies. In addition, the dominance of the waves in the range is also verified
by the small frequency deviation from the linear dispersion relation. In the
wave-dominant range, the linear wave periods given by the linear dispersion
relation are smaller than approximately one third of the eddy-turnover time.
The linear wave periods reflect the anisotropy of the system, while the
isotropic Brunt-V\"ais\"al\"a period is used to evaluate the Ozmidov wave
number, which is necessarily isotropic. It is found that the time scales in
consideration of the anisotropy of the flow field must be appropriately
selected to obtain the critical wave number separating the weak-wave
turbulence.
