Vowels are capable of being continued during a longer or shorter period. All English vowels (with the exception of diphthongs) are generally divided into long and short.
In the similarly accented position all English vowels are fully long when they are final, eg. see. They are almost as long as that when a weak voiced consonant follows them in the closed syllable, eg. seed. They are considerably shorter before strong voiceless consonants in closed syllables, eg. seat.
All English vowels are longer when they are strongly stressed and when they are in the nuclear syllable, eg. brass.