A is for (whoever gets Z starts the next theme)

[twyngwyn]

Grows on a tree

A is for Almond

[purple_haize]

X is for X train crossing

[electric*mayhem*band]

Y -

Z is for Zebra Crossing.

Next theme: Synonyms - Two words meaning the same.

A is for Ache / Pain.

[cq_tech]

B is for Basement / Cellar

[electric*mayhem*band]

C is for Cumulative / Increasing.

[crosbystills]

D is for Deadly / Lethal

[purple_haize]

E is for End / Last

[crosbystills]

F is for Fast / Swift

[twyngwyn]

G is for Glue / Gum

[purple_haize]

H is for Hello / Hi

[youcandoityoucandoityoucandoit]

I is for Ingenious / clever