The word "Oestrasid" is a challenging word to spell. It refers to a family of fish species that live in the sea. The phonetic transcription of this word is ˈi:strəsɪd, which indicates that there are two syllables in the word, and the first syllable has a long "ee" sound. The spelling of this word can be confusing because it contains the letter "o" but is pronounced with a long "ee" sound. This is because "oestr" is a common prefix in biology that refers to estrus, a female reproductive cycle.