voiceless labiodental [f]ricatives...

The word truck begins with a simple sound...[tr].  My two-year old nephew has yet to master this linguistic harmony.  He is also working on the sound [cr], another similar phonetic puzzle. 

Yesterday, as he played with a little yellow truck, and later described a wooden crocodile I bit my lips and smiled.  In an effort to master those sounds, [tr] and [cr]...it seems that he has settled on the [f] sound.  

(You will work it out and perhaps bite your lips...and smile.)