Ar can be used when the prefix a- precedes a root word beginning with r.
Ea can be used with the suffixes -al, -an or -ate and a root word ending in e.
Contractions containing a, e or o can be used with a prefix or suffix that is not part of a diphthong or diaeresis ae or oe.
Contractions are not to be used when they would alter a root or base word with an affix.
but not 
Contractions are not to be used in a root with an affix if the contraction would not be used in the root word without the affix.
but not because is wrong.
Exceptions are 
and 
.
Contractions are not to be used across affixes and roots, across compound words, or across consonants pronounced separately.
but not
but not 
but not
Contractions should not be used in diphthong or diaeresis ae or oe, or in ee followed by a, oi followed by ty, oo followed by ne or eau preceded by bl.
but not
but not 
Exceptions are , 
and .
Contractions should not be used when their use causes difficulty in pronunciation or breaking up a consonantal diphthong or triphthong.
but not
but not 
rather than 
Choose the rendering containing and, for, the, of or with, unless doing so takes up more space.
rather than 
rather than
One-celled contractions are preferred over two-celled contractions.
rather than 
Exceptions are ence used before d or r.
rather than
Renderings that avoid double letters (bb cc dd ff gg) and ea are preferred.
rather than 
In all other cases, preference is given to the rendering that more closely approximates the pronunciation of the word.
rather than 
