Acronym	Meaning and Definition
Angle_1	The neck-flexion angle between the global horizontal and the vector pointing from C7 vertebra to the occipito-cervical joint.
Angle_2	The neck-flexion angle between the global horizontal and the vector pointing from C1 vertebra to the occipito-cervical joint.
C1, C7	Neck vertebrae
C4.5	DT algorithm named C4.5
DT	Decision tree
E	Entropy
FFT	Fast Fourier transform
FN	False negative
FP	False positive
GLCM	Gray-level co-occurrence matrix (GLCM)
IG	Information gain
ML	Machine learning
NDI	Neck disability index
NP	Neck pain
RMSE	Root mean square error
ROC	Receiver operating characteristic
SM	Social media
Std. Error	Standard error
STDev	Standard deviation
TN	True negative
TP	True positive
VAS	Visual analogue scale
WHO	World health organization