Complex sentence: Real transformers have losses, nonlinearties, and complex fields that do not lend themselves to convenient analysis; ideal transformers have nice qualities, but lack the elements of interest, in this case leakage inductances.
Split into simpler sentences: Real transformers have losses, nonlinearties, and complex fields that do not lend themselves to convenient analysis. Ideal transformers have nice qualities, but lack the elements of interest, in this case leakage inductances.