O que são contrações em Inglês?

Esses termos são aceitos em textos técnicos? Formais?

O inglês informal, seja o falado ou o escrito, costuma ter contrações inúmeras. Algumas costumam causar dúvidas, outras são mais simples. No entanto, muita gente se confunde bastante com elas.O inglês é uma língua que usa a forma contrata em muitas estruturas tornando-as mais reduzidas. Por exemplo, em vez de dizer “She will come” (Ela virá), o mais comum é dizer “She’ll come”. Além do “will” reduzimos também:

    “verb to be” (I am = I’m / He is = He’s / They are = They’re).
    “have” no present perfect (I have been there. = I’ve been there.).
    “had” no past perfect (I had never seen it. = I’d never seen it.).
    “would” (I would love it. = I’d love it.).      
       
Alguns exemplos:
I'm --- I am --- Example: I'm waiting for my friend.
I'll --- I will --- Example: I'll see you tomorrow.
I'd --- I had / I would --- Example: I'd better leave now. OR I'd already eaten by the time he arrived.
I've --- I have --- Example: I've worked here for many years.
You're --- You are --- Example: You're joking!
You'll --- You will --- Example: You'll be sorry!
You'd --- You had / would --- Example: You'd left before he arrived, hadn't you? OR You'd better hurry up.
You've --- You have --- Example: You've been to London many times.
He's --- He is / has --- Example: He's on the phone now. OR He's been playing tennis since 10 this morning.
He'll --- He will --- Example: He'll be here tomorrow.
He'd --- He had / would --- Example: He'd prefer to meet you later in the week. OR He'd finished before the meeting began.
She's --- She is / has --- Example: She's watching TV at the moment. OR She's had a lot of trouble lately.
She'll --- She will --- Example: She'll be at the meeting.
She'd --- She had / would --- Example: She'd been working for two hours when he telephoned. OR She'd like to have a glass of wine.
It's --- It is / has --- Example: It's been long time since we saw each other last. OR It's very difficult to concentrate.
It'll --- It will --- Example: It'll be here soon.
It'd --- It would / had --- Example: It'd be difficult to say no. OR It'd been a long time.
We're --- We are --- Example: We're working hard on the Smith account this week.
We'll --- We will --- Example: We'll begin when he arrives.
We'd --- We had / would --- Example: We'd better hurry up if we want to catch the train. OR We'd finished the meeting before you arrived.