The "y" sound:
* In "bicycle," the "y" is pronounced as a consonant sound. This is because the "y" is followed by a vowel ("i"). In this case, it's pronounced as a "bi" sound, similar to the "y" in "yes" or "yellow."
* In "motorcycle," the "y" is not pronounced at all. It acts as a silent letter. This is because the "y" is followed by a consonant ("c").
The reasons for the difference:
* Historical evolution: English pronunciation has changed drastically over time. The "y" sound in "bicycle" reflects an older pronunciation pattern.
* Influence of French: The word "bicycle" is derived from French "bicyclette," where the "y" is pronounced as a consonant.
* Phonetic rules: In general, the "y" sound is more common in words where it's followed by a vowel. This is a simplification of a more complex set of rules governing consonant and vowel sounds.
The bottom line: The difference in pronunciation is due to a combination of historical, linguistic, and phonetic factors. It's simply one of those quirks of English!