"Ratio" and "proportion" confusions

The ratio of any number of quantities is a quantitative comparison of their measures.

In particular, the binary ratio $T:H$ is equivalent to the fraction $\displaystyle\frac TH.$

Variables $T$ and $H$ being in (direct) proportion means that as they vary, $$\frac {T_1}{H_1}=\frac {T_2}{H_2}=\frac {T_i}{H_i}.$$ Thus, direct proportion equates ratios of pairs of corresponding values.

We can also say that the pairs of corresponding values $(T_i,H_i)$ are in (direct) proportion.

Variables $T$ and $H$ being in inverse proportion means that as they vary, $$T_1H_1=T_2H_2=T_iH_i.$$

In less technical contexts, proportion simply means a proper fraction or a percentage smaller than $100\%.$