An encouraging word is moral-support, which is felt, as well as heard.
It makes all of the difference, it helps one form perseverance and build much needed resilience.
It may very well be "that little push," which saves that person's day, and it may very well be a brightly coloured rainbow, or a ray of sunshine, which chases their dark clouds away.
It's an empathetic, invisible, warm embrace, it's a smile that says... "You're not alone," which is warmly written all over your face.
An encouraging word is humble kindness, which is most appreciated, whilst it is being observed.