An interesting method to define the right usage of the right term is to ask a question if the person who is undertaking research in a particular field is a scientist or a scholar.
Someone whose expertise is in medieval literature would never be called a scientist, but the correct term to describe her/him will be a scholar. So the activities in the field of medieval literature are scholarly activities not scientific. Will someone engaged in research activities in the field of bioengineering be called a scholar? Of course no, and the correct term to describe her/him will be a scientist. And, just as in the case of the usage of the term “academic”, to describe someone, regardless the field of activities the term “academician” may be used and anyone engaged in any academic activities in humanities or exact sciences may be called an “academician”.
To conclude the terms “scientific” and “scientist” are used to identify and describe an event, activity or a person engaged in natural/exact sciences. The terms “scholarly” and “scholar” are used to identify events and people in the fields of humanities and social sciences. And, the terms “academic” and “academician” may identify and describe any person or event in any field of research activities. Anytime the context is doubtful it will be a correct decision to use the term “academic” and “academician” to avoid misunderstandings and to sound academic.
Science is a relatively new word. As indeed is "academic" which is a Romantic usage, referring to the school of philosophers in Athens led by Plato and Aristotle, which gained its name because the members met in an arcade. Those who practice science were always referred to as, "natural philosophers" until the last couple of centuries, meaning originally that they studied the, natural material world, and used material methods. I. Newton would probably for example, have referred to his work most often as natural philosophy.
Today the word scientist is usually taken to mean not merely natural philosopher, but also someone who uses the scientific method as well. Which is a vague, ill defined term, often disputed, but would generally be thought to include such ideas as, nothing being ever totally proven, repeatable results, experimental results being more important than hypothesis, and testing against disproof, plus a few other bits like peer review and the ranking of hypothesis, theory, mathematical proof.