An English sonnet almost always has 14 lines; and is usually in Iambic Pentameter.

Shorter sonnets exist (G M Hopkins' Curtal Sonnets - including Pied Beauty - are among the best known) - but they are very rare. Sonnets longer than fourteen lines are even rarer.

The bassoon.

sonnet

Sonnet 18 and sonnet 116

Sonnets always have 14 lines. The difference is in their format. The Shakespearean(or Elizabethean) sonnet has 3 quatrains which means 3 'blocks' of 4 lines and at the end it has 2 lines (a duet). A suggested rhyme scheme could be ABAB CDCD EFEF GG. ABAB is one quatrain.

The Italian sonnet on the other hand consists of an octet followed by a sestet. An octet is a ''block'' of 8 lines and a sestet is a ''block'' of six lines.

Notice that in a sonnet these 'blocks' don't have a line being skipped between them, they are just the way in which they are grouped.