The terms lawful and legal differ in that the former contemplates the substance of law, whereas the latter alludes to the form of law. A lawful act is authorized, sanctioned, or not forbidden by law. A legal act is performed in accordance with the forms and usages of law, or in a technical manner. In this sense, illegal approaches the meaning of invalid. For example, a contract or will, executed without the required formalities, might be regarded as invalid or illegal, but could not be described as unlawful. The term lawful more clearly suggests an ethical content than does the word legal. The latter merely denotes compliance with technical or formal rules, whereas the former usually signifies a moral substance or ethical permissibility. An additional distinction is that the word legal is used as the synonym of constructive, while lawful is not. Legal fraud is Fraud implied by law, or made out by construction, but lawful fraud would be a contradiction in terms. Legal is also used as the antithesis of equitable, just. As a result, legal estate is the correct usage, instead of lawful estate. Under certain circumstances, however, the two words are used as exact equivalents. A lawful writ, warrant, or process is the same as a legal writ, warrant, or process. legitimate adj., adv.: 1) legal, proper, real. 2) referring to a child born to parents who are married. A baby born to parents who are not married is illegitimate, but can be made legitimate (legitimatized) by the subsequent marriage of the parents. 3) v. to make proper and/or legal. Copyright © 1981-2005 by Gerald N. Hill and Kathleen T. Hill. All Right reserved. LEGITIMATE. That which is according to law; as, legitimate children, are lawful children, born in wedlock, in contradistinction to bastards; legitimate authority, or lawful power, in opposition to usurpation. http://legal-dictionary.thefreedictionary.com/legitimate

They can all mean exactly the same thing depending on the context. Is the business legal? is the business lawful? Is the business legitimate? Could all mean the same thing. Some of the words have other meanings though. 'Legal' can mean related to the law. So if you talk about a 'legal business' it could mean the same as a 'lawful business' but it could also mean a business connected to the law such as a firm of lawyers. Also 'legitimate' can mean that something that has a fair and acceptable reason. Thus if you spoke about a 'legitimate business' it could mean the same as lawful business but it could also mean an 'acceptable' business. A company selling very expensive poor quality goods might be 'lawful' but in one sense it is not legitmate because it will lose money and go bankrupt. If that sounds complicated, don't worry! You can usually tell which one they mean from the context

EDIT - I see the question has already been answered excellently and detailed, but I´ll let my examples stand... "It is legal to drink alcohol from the age of 18", "It is illegal to drink and drive" "He is the lawful heir.", "She is my lawfully wedded wife" "You have a legitimate concern" - meaning you have a good reason to be concerned.

You could look at this website! There's a great explanation there on this website. askit4equity.com https://askit4equity.com/legal-v-lawful/