This is an explanation about describing a line graph. If any mistakes happens please apologize.
List of words :
Increase - rise / increase / uplift / upsurge/ soar/ improve/ move upward/ soar/ surge

Decrease - fall / decrease / decline / plunge/ drop / reduce / collapse / deteriorate/ go down

Steadiness unchanged / remain constant / remain steady / plateau / remain the same / remain stable / remain static a steadiness/ a plateau / a stability/ a static

Rapid change - dramatically / rapidly / sharply / quickly / hurriedly / speedily / swiftly / significantly/ considerably / substantially / noticeably

Moderate change - moderately / gradually / progressively / sequentially

Steady change - steadily/ ceaselessly

Slight change -slightly / slowly / mildly / tediously.

Rapid ups and downs -wave / fluctuate / oscillate / vacillate / palpitate