$6\mathrm{.}1$ Define what is meant by $($a$)$ energy $($refer back to Chapter $4)$; $($b$)$ total energy; $($c$)$ head; $($d$)$ total energy; $($e$)$ total head line; $($f$)$ piezometric level; $($g$)$ hydraulic gradient; $($h$)$ hydraulic grade line; and $($i$)$ minor loss.