It appears, at least according to the following, that the definitions may have changed over the past almost 40 years...
"1957
The first published definition for Army Warrant Officers was established in AR 611-112 and defined the warrant officer as follows:
"The warrant officer is a highly skilled technician who is provided to fill those positions above the enlisted level which are too specialized in scope to permit effective development and continued utilization of broadly trained, branch qualified commissioned officers."
(The above would seem to indicate differences between the two)
1985
In 1985 the Army developed a clear and concise definition of the Warrant Officer that encompassed all warrant officer specialties.
"An officer
appointed by warrant by the Secretary of the Army, based upon a sound level of technical and tactical competence. The warrant officer is the highly specialized expert and trainer who, by gaining progressive levels of expertise and leadership, operates, maintains, administers, and manages the Army’s equipment, support activities, or technical systems for an entire career." (Para 1-7 DA Pamphlet 600-11)
(Same here)
1996
Department of the Army Pamphlet 600-11, Warrant Officer Professional Development, dated 30 December 1996, defines an Army Warrant Officer as:
"An officer
appointed by warrant by the Secretary of the Army, based upon a sound level of technical and tactical competence. The warrant officer is the highly specialized expert and trainer who, by gaining progressive levels of expertise and leadership, operates, maintains, administers, and manages the Army’s equipment, support activities, or technical systems for an entire career." (Para 1-7 DA Pamphlet 600-11)
1999
Army Field Manual 22-100, Army Leadership, 31 August 1999, explains the role of Army Warrant Officers as:
"Warrant officers are highly specialized, single-track specialty officers who receive their authority from the Secretary of the Army upon their initial appointment. However, Title 10 U.S.C. authorizes the
commissioning of warrant officers (WO1) upon promotion to chief warrant officer (CW2). These commissioned warrant officers are direct representatives of the President of the United States. They derive their authority from the same source as commissioned officers but remain specialists, in contrast to commissioned officers, who are generalists. Warrant officers can and do command detachments, units, activities, and vessels as well as lead, coach, train, and counsel subordinates. As leaders and technical experts, they provide valuable skills, guidance, and expertise to commanders and organizations in their particular field." (Para A-3, Field Manual 22-100)
(This is the first time the term "commissioning" is used, so while it's still not completely clear, we used to consider that the Warrant Officer received a "Warrant" not a "Commission." Perhaps that has been changed in the interim.)