Many of the AMS mathematical display environments are designed to give the user greater or complete control of structural layout. The typesetting nature of the environments is so strong that using these can be problematic as the user may rely on the layout to convey information or to guide the reader. The transformations to large print which reflow and can lose alignment and any speech output will not convey the original structure. While some environments are included as possibilities these effects must be recalled and output proofread.
\tag cannot be used; neither can \notag cannot be used — use \nonumber instead if necessary.
All comments about eqnarray above hold in these environments excepting that there is no requirement to include any number of ampersands.