Hello, can you tell me please what this means: יישר כוח? I read this: יישר כוח can you tell me the literal translation and the regular one as well please? thank you!

Trickle vs Waterjet? Hello Could you please explain me the difference between "trickle" and "waterjet" and show some examples of their use? Thank you!

Is this well written? Hello! I wanna know if this idea is right: "He has written asking Santa Claus for a gift", implying that he has written a letter, but without mentioning that. Should I write it in a different way? Thank you!

uses of the word "espouse" Hello! I wanted to know if the word "espouse" can be a synonym of "defend" and if so can you use it in a sentence? If there's a better meaning please tell me so.

What is "medical film"? I saw the term "medical film" the other day, I understand it refers to the material used to take x-ray pictures. Is that so? does it have another name? Thanx.

What does "slickest gig" mean? In the song "the Surrey with the Fringe on top" from the Oklahoma musical, when they sing: You will set behind a team of snow white horses, In the slickest gig you ever see! What does the words "slickest gig" mean? And also what's "Surrey" and what's "Fringe"? Apparently Surrey is a place in UK and Fringe is like an edge, but is not making sense to me: "When I take you out in the surrey with the fringe on top!" Anyone could help?

What does "tis" mean in the song "Danny boy"? There's a song called "Danny boy" and I looked for the word meanings but I couldn't find the meaning of the word "tis" when it says: The summer's gone, and all the flowers are dying 'Tis you, 'tis you must go and I must bide. I assume it is a contraction of a word, does anybody know?