If one amount is ~ to another, the two amounts increase and decrease at the same rate so there is always the same relationship between them. (FORMAL)
Loss of weight is directly ~ to the rate at which the disease is progressing.
ADJ: usu v-link ADJ to n
~ly
You have ~ly more fat on your thighs and hips than anywhere else on your body...
ADV: ADV with v, ADV with cl/group